test_window.py

from collections import OrderedDict
from datetime import datetime, timedelta
from itertools import product
import warnings
from warnings import catch_warnings

import numpy as np
from numpy.random import randn
import pytest

from pandas.errors import UnsupportedFunctionCall
import pandas.util._test_decorators as td

import pandas as pd
from pandas import DataFrame, Index, Series, Timestamp, bdate_range, concat, isna, notna
from pandas.core.base import DataError, SpecificationError
from pandas.core.sorting import safe_sort
import pandas.core.window as rwindow
import pandas.util.testing as tm

import pandas.tseries.offsets as offsets

N, K = 100, 10


def assert_equal(left, right):
    if isinstance(left, Series):
        tm.assert_series_equal(left, right)
    else:
        tm.assert_frame_equal(left, right)


@pytest.fixture(params=[True, False])
def raw(request):
    return request.param


@pytest.fixture(
    params=[
        "triang",
        "blackman",
        "hamming",
        "bartlett",
        "bohman",
        "blackmanharris",
        "nuttall",
        "barthann",
    ]
)
def win_types(request):
    return request.param


@pytest.fixture(params=["kaiser", "gaussian", "general_gaussian", "exponential"])
def win_types_special(request):
    return request.param


@pytest.fixture(
    params=["sum", "mean", "median", "max", "min", "var", "std", "kurt", "skew"]
)
def arithmetic_win_operators(request):
    return request.param


class Base:

    _nan_locs = np.arange(20, 40)
    _inf_locs = np.array([])

    def _create_data(self):
        arr = randn(N)
        arr[self._nan_locs] = np.NaN

        self.arr = arr
        self.rng = bdate_range(datetime(2009, 1, 1), periods=N)
        self.series = Series(arr.copy(), index=self.rng)
        self.frame = DataFrame(randn(N, K), index=self.rng, columns=np.arange(K))


class TestApi(Base):
    def setup_method(self, method):
        self._create_data()

    def test_getitem(self):

        r = self.frame.rolling(window=5)
        tm.assert_index_equal(r._selected_obj.columns, self.frame.columns)

        r = self.frame.rolling(window=5)[1]
        assert r._selected_obj.name == self.frame.columns[1]

        # technically this is allowed
        r = self.frame.rolling(window=5)[1, 3]
        tm.assert_index_equal(r._selected_obj.columns, self.frame.columns[[1, 3]])

        r = self.frame.rolling(window=5)[[1, 3]]
        tm.assert_index_equal(r._selected_obj.columns, self.frame.columns[[1, 3]])

    def test_select_bad_cols(self):
        df = DataFrame([[1, 2]], columns=["A", "B"])
        g = df.rolling(window=5)
        with pytest.raises(KeyError, match="Columns not found: 'C'"):
            g[["C"]]
        with pytest.raises(KeyError, match="^[^A]+$"):
            # A should not be referenced as a bad column...
            # will have to rethink regex if you change message!
            g[["A", "C"]]

    def test_attribute_access(self):

        df = DataFrame([[1, 2]], columns=["A", "B"])
        r = df.rolling(window=5)
        tm.assert_series_equal(r.A.sum(), r["A"].sum())
        msg = "'Rolling' object has no attribute 'F'"
        with pytest.raises(AttributeError, match=msg):
            r.F

    def tests_skip_nuisance(self):

        df = DataFrame({"A": range(5), "B": range(5, 10), "C": "foo"})
        r = df.rolling(window=3)
        result = r[["A", "B"]].sum()
        expected = DataFrame(
            {"A": [np.nan, np.nan, 3, 6, 9], "B": [np.nan, np.nan, 18, 21, 24]},
            columns=list("AB"),
        )
        tm.assert_frame_equal(result, expected)

    def test_skip_sum_object_raises(self):
        df = DataFrame({"A": range(5), "B": range(5, 10), "C": "foo"})
        r = df.rolling(window=3)
        result = r.sum()
        expected = DataFrame(
            {"A": [np.nan, np.nan, 3, 6, 9], "B": [np.nan, np.nan, 18, 21, 24]},
            columns=list("AB"),
        )
        tm.assert_frame_equal(result, expected)

    def test_agg(self):
        df = DataFrame({"A": range(5), "B": range(0, 10, 2)})

        r = df.rolling(window=3)
        a_mean = r["A"].mean()
        a_std = r["A"].std()
        a_sum = r["A"].sum()
        b_mean = r["B"].mean()
        b_std = r["B"].std()
        b_sum = r["B"].sum()

        result = r.aggregate([np.mean, np.std])
        expected = concat([a_mean, a_std, b_mean, b_std], axis=1)
        expected.columns = pd.MultiIndex.from_product([["A", "B"], ["mean", "std"]])
        tm.assert_frame_equal(result, expected)

        result = r.aggregate({"A": np.mean, "B": np.std})

        expected = concat([a_mean, b_std], axis=1)
        tm.assert_frame_equal(result, expected, check_like=True)

        result = r.aggregate({"A": ["mean", "std"]})
        expected = concat([a_mean, a_std], axis=1)
        expected.columns = pd.MultiIndex.from_tuples([("A", "mean"), ("A", "std")])
        tm.assert_frame_equal(result, expected)

        result = r["A"].aggregate(["mean", "sum"])
        expected = concat([a_mean, a_sum], axis=1)
        expected.columns = ["mean", "sum"]
        tm.assert_frame_equal(result, expected)

        with catch_warnings(record=True):
            # using a dict with renaming
            warnings.simplefilter("ignore", FutureWarning)
            result = r.aggregate({"A": {"mean": "mean", "sum": "sum"}})
        expected = concat([a_mean, a_sum], axis=1)
        expected.columns = pd.MultiIndex.from_tuples([("A", "mean"), ("A", "sum")])
        tm.assert_frame_equal(result, expected, check_like=True)

        with catch_warnings(record=True):
            warnings.simplefilter("ignore", FutureWarning)
            result = r.aggregate(
                {
                    "A": {"mean": "mean", "sum": "sum"},
                    "B": {"mean2": "mean", "sum2": "sum"},
                }
            )
        expected = concat([a_mean, a_sum, b_mean, b_sum], axis=1)
        exp_cols = [("A", "mean"), ("A", "sum"), ("B", "mean2"), ("B", "sum2")]
        expected.columns = pd.MultiIndex.from_tuples(exp_cols)
        tm.assert_frame_equal(result, expected, check_like=True)

        result = r.aggregate({"A": ["mean", "std"], "B": ["mean", "std"]})
        expected = concat([a_mean, a_std, b_mean, b_std], axis=1)

        exp_cols = [("A", "mean"), ("A", "std"), ("B", "mean"), ("B", "std")]
        expected.columns = pd.MultiIndex.from_tuples(exp_cols)
        tm.assert_frame_equal(result, expected, check_like=True)

    def test_agg_apply(self, raw):

        # passed lambda
        df = DataFrame({"A": range(5), "B": range(0, 10, 2)})

        r = df.rolling(window=3)
        a_sum = r["A"].sum()

        result = r.agg({"A": np.sum, "B": lambda x: np.std(x, ddof=1)})
        rcustom = r["B"].apply(lambda x: np.std(x, ddof=1), raw=raw)
        expected = concat([a_sum, rcustom], axis=1)
        tm.assert_frame_equal(result, expected, check_like=True)

    def test_agg_consistency(self):

        df = DataFrame({"A": range(5), "B": range(0, 10, 2)})
        r = df.rolling(window=3)

        result = r.agg([np.sum, np.mean]).columns
        expected = pd.MultiIndex.from_product([list("AB"), ["sum", "mean"]])
        tm.assert_index_equal(result, expected)

        result = r["A"].agg([np.sum, np.mean]).columns
        expected = Index(["sum", "mean"])
        tm.assert_index_equal(result, expected)

        result = r.agg({"A": [np.sum, np.mean]}).columns
        expected = pd.MultiIndex.from_tuples([("A", "sum"), ("A", "mean")])
        tm.assert_index_equal(result, expected)

    def test_agg_nested_dicts(self):

        # API change for disallowing these types of nested dicts
        df = DataFrame({"A": range(5), "B": range(0, 10, 2)})
        r = df.rolling(window=3)

        msg = r"cannot perform renaming for (r1|r2) with a nested dictionary"
        with pytest.raises(SpecificationError, match=msg):
            r.aggregate({"r1": {"A": ["mean", "sum"]}, "r2": {"B": ["mean", "sum"]}})

        expected = concat(
            [r["A"].mean(), r["A"].std(), r["B"].mean(), r["B"].std()], axis=1
        )
        expected.columns = pd.MultiIndex.from_tuples(
            [("ra", "mean"), ("ra", "std"), ("rb", "mean"), ("rb", "std")]
        )
        with catch_warnings(record=True):
            warnings.simplefilter("ignore", FutureWarning)
            result = r[["A", "B"]].agg(
                {"A": {"ra": ["mean", "std"]}, "B": {"rb": ["mean", "std"]}}
            )
        tm.assert_frame_equal(result, expected, check_like=True)

        with catch_warnings(record=True):
            warnings.simplefilter("ignore", FutureWarning)
            result = r.agg({"A": {"ra": ["mean", "std"]}, "B": {"rb": ["mean", "std"]}})
        expected.columns = pd.MultiIndex.from_tuples(
            [
                ("A", "ra", "mean"),
                ("A", "ra", "std"),
                ("B", "rb", "mean"),
                ("B", "rb", "std"),
            ]
        )
        tm.assert_frame_equal(result, expected, check_like=True)

    def test_count_nonnumeric_types(self):
        # GH12541
        cols = [
            "int",
            "float",
            "string",
            "datetime",
            "timedelta",
            "periods",
            "fl_inf",
            "fl_nan",
            "str_nan",
            "dt_nat",
            "periods_nat",
        ]

        df = DataFrame(
            {
                "int": [1, 2, 3],
                "float": [4.0, 5.0, 6.0],
                "string": list("abc"),
                "datetime": pd.date_range("20170101", periods=3),
                "timedelta": pd.timedelta_range("1 s", periods=3, freq="s"),
                "periods": [
                    pd.Period("2012-01"),
                    pd.Period("2012-02"),
                    pd.Period("2012-03"),
                ],
                "fl_inf": [1.0, 2.0, np.Inf],
                "fl_nan": [1.0, 2.0, np.NaN],
                "str_nan": ["aa", "bb", np.NaN],
                "dt_nat": [
                    Timestamp("20170101"),
                    Timestamp("20170203"),
                    Timestamp(None),
                ],
                "periods_nat": [
                    pd.Period("2012-01"),
                    pd.Period("2012-02"),
                    pd.Period(None),
                ],
            },
            columns=cols,
        )

        expected = DataFrame(
            {
                "int": [1.0, 2.0, 2.0],
                "float": [1.0, 2.0, 2.0],
                "string": [1.0, 2.0, 2.0],
                "datetime": [1.0, 2.0, 2.0],
                "timedelta": [1.0, 2.0, 2.0],
                "periods": [1.0, 2.0, 2.0],
                "fl_inf": [1.0, 2.0, 2.0],
                "fl_nan": [1.0, 2.0, 1.0],
                "str_nan": [1.0, 2.0, 1.0],
                "dt_nat": [1.0, 2.0, 1.0],
                "periods_nat": [1.0, 2.0, 1.0],
            },
            columns=cols,
        )

        result = df.rolling(window=2).count()
        tm.assert_frame_equal(result, expected)

        result = df.rolling(1).count()
        expected = df.notna().astype(float)
        tm.assert_frame_equal(result, expected)

    @td.skip_if_no_scipy
    @pytest.mark.filterwarnings("ignore:can't resolve:ImportWarning")
    def test_window_with_args(self):
        # make sure that we are aggregating window functions correctly with arg
        r = Series(np.random.randn(100)).rolling(
            window=10, min_periods=1, win_type="gaussian"
        )
        expected = concat([r.mean(std=10), r.mean(std=0.01)], axis=1)
        expected.columns = ["<lambda>", "<lambda>"]
        result = r.aggregate([lambda x: x.mean(std=10), lambda x: x.mean(std=0.01)])
        tm.assert_frame_equal(result, expected)

        def a(x):
            return x.mean(std=10)

        def b(x):
            return x.mean(std=0.01)

        expected = concat([r.mean(std=10), r.mean(std=0.01)], axis=1)
        expected.columns = ["a", "b"]
        result = r.aggregate([a, b])
        tm.assert_frame_equal(result, expected)

    def test_preserve_metadata(self):
        # GH 10565
        s = Series(np.arange(100), name="foo")

        s2 = s.rolling(30).sum()
        s3 = s.rolling(20).sum()
        assert s2.name == "foo"
        assert s3.name == "foo"

    @pytest.mark.parametrize(
        "func,window_size,expected_vals",
        [
            (
                "rolling",
                2,
                [
                    [np.nan, np.nan, np.nan, np.nan],
                    [15.0, 20.0, 25.0, 20.0],
                    [25.0, 30.0, 35.0, 30.0],
                    [np.nan, np.nan, np.nan, np.nan],
                    [20.0, 30.0, 35.0, 30.0],
                    [35.0, 40.0, 60.0, 40.0],
                    [60.0, 80.0, 85.0, 80],
                ],
            ),
            (
                "expanding",
                None,
                [
                    [10.0, 10.0, 20.0, 20.0],
                    [15.0, 20.0, 25.0, 20.0],
                    [20.0, 30.0, 30.0, 20.0],
                    [10.0, 10.0, 30.0, 30.0],
                    [20.0, 30.0, 35.0, 30.0],
                    [26.666667, 40.0, 50.0, 30.0],
                    [40.0, 80.0, 60.0, 30.0],
                ],
            ),
        ],
    )
    def test_multiple_agg_funcs(self, func, window_size, expected_vals):
        # GH 15072
        df = pd.DataFrame(
            [
                ["A", 10, 20],
                ["A", 20, 30],
                ["A", 30, 40],
                ["B", 10, 30],
                ["B", 30, 40],
                ["B", 40, 80],
                ["B", 80, 90],
            ],
            columns=["stock", "low", "high"],
        )

        f = getattr(df.groupby("stock"), func)
        if window_size:
            window = f(window_size)
        else:
            window = f()

        index = pd.MultiIndex.from_tuples(
            [("A", 0), ("A", 1), ("A", 2), ("B", 3), ("B", 4), ("B", 5), ("B", 6)],
            names=["stock", None],
        )
        columns = pd.MultiIndex.from_tuples(
            [("low", "mean"), ("low", "max"), ("high", "mean"), ("high", "min")]
        )
        expected = pd.DataFrame(expected_vals, index=index, columns=columns)

        result = window.agg(
            OrderedDict((("low", ["mean", "max"]), ("high", ["mean", "min"])))
        )

        tm.assert_frame_equal(result, expected)


@pytest.mark.filterwarnings("ignore:can't resolve package:ImportWarning")
class TestWindow(Base):
    def setup_method(self, method):
        self._create_data()

    @td.skip_if_no_scipy
    @pytest.mark.parametrize("which", ["series", "frame"])
    def test_constructor(self, which):
        # GH 12669

        o = getattr(self, which)
        c = o.rolling

        # valid
        c(win_type="boxcar", window=2, min_periods=1)
        c(win_type="boxcar", window=2, min_periods=1, center=True)
        c(win_type="boxcar", window=2, min_periods=1, center=False)

        # not valid
        for w in [2.0, "foo", np.array([2])]:
            with pytest.raises(ValueError):
                c(win_type="boxcar", window=2, min_periods=w)
            with pytest.raises(ValueError):
                c(win_type="boxcar", window=2, min_periods=1, center=w)

        for wt in ["foobar", 1]:
            with pytest.raises(ValueError):
                c(win_type=wt, window=2)

    @td.skip_if_no_scipy
    @pytest.mark.parametrize("which", ["series", "frame"])
    def test_constructor_with_win_type(self, which, win_types):
        # GH 12669
        o = getattr(self, which)
        c = o.rolling
        c(win_type=win_types, window=2)

    @pytest.mark.parametrize("method", ["sum", "mean"])
    def test_numpy_compat(self, method):
        # see gh-12811
        w = rwindow.Window(Series([2, 4, 6]), window=[0, 2])

        msg = "numpy operations are not valid with window objects"

        with pytest.raises(UnsupportedFunctionCall, match=msg):
            getattr(w, method)(1, 2, 3)
        with pytest.raises(UnsupportedFunctionCall, match=msg):
            getattr(w, method)(dtype=np.float64)

    @td.skip_if_no_scipy
    @pytest.mark.parametrize("arg", ["median", "var", "std"])
    def test_agg_function_support(self, arg):
        df = pd.DataFrame({"A": np.arange(5)})
        roll = df.rolling(2, win_type="triang")

        msg = "'{arg}' is not a valid function for " "'Window' object".format(arg=arg)
        with pytest.raises(AttributeError, match=msg):
            roll.agg(arg)

        with pytest.raises(AttributeError, match=msg):
            roll.agg([arg])

        with pytest.raises(AttributeError, match=msg):
            roll.agg({"A": arg})


class TestRolling(Base):
    def setup_method(self, method):
        self._create_data()

    def test_doc_string(self):

        df = DataFrame({"B": [0, 1, 2, np.nan, 4]})
        df
        df.rolling(2).sum()
        df.rolling(2, min_periods=1).sum()

    @pytest.mark.parametrize("which", ["series", "frame"])
    def test_constructor(self, which):
        # GH 12669

        o = getattr(self, which)
        c = o.rolling

        # valid
        c(window=2)
        c(window=2, min_periods=1)
        c(window=2, min_periods=1, center=True)
        c(window=2, min_periods=1, center=False)

        # GH 13383
        with pytest.raises(ValueError):
            c(0)
            c(-1)

        # not valid
        for w in [2.0, "foo", np.array([2])]:
            with pytest.raises(ValueError):
                c(window=w)
            with pytest.raises(ValueError):
                c(window=2, min_periods=w)
            with pytest.raises(ValueError):
                c(window=2, min_periods=1, center=w)

    @td.skip_if_no_scipy
    @pytest.mark.parametrize("which", ["series", "frame"])
    def test_constructor_with_win_type(self, which):
        # GH 13383
        o = getattr(self, which)
        c = o.rolling
        with pytest.raises(ValueError):
            c(-1, win_type="boxcar")

    @pytest.mark.parametrize("window", [timedelta(days=3), pd.Timedelta(days=3)])
    def test_constructor_with_timedelta_window(self, window):
        # GH 15440
        n = 10
        df = DataFrame(
            {"value": np.arange(n)},
            index=pd.date_range("2015-12-24", periods=n, freq="D"),
        )
        expected_data = np.append([0.0, 1.0], np.arange(3.0, 27.0, 3))

        result = df.rolling(window=window).sum()
        expected = DataFrame(
            {"value": expected_data},
            index=pd.date_range("2015-12-24", periods=n, freq="D"),
        )
        tm.assert_frame_equal(result, expected)
        expected = df.rolling("3D").sum()
        tm.assert_frame_equal(result, expected)

    @pytest.mark.parametrize("window", [timedelta(days=3), pd.Timedelta(days=3), "3D"])
    def test_constructor_timedelta_window_and_minperiods(self, window, raw):
        # GH 15305
        n = 10
        df = DataFrame(
            {"value": np.arange(n)},
            index=pd.date_range("2017-08-08", periods=n, freq="D"),
        )
        expected = DataFrame(
            {"value": np.append([np.NaN, 1.0], np.arange(3.0, 27.0, 3))},
            index=pd.date_range("2017-08-08", periods=n, freq="D"),
        )
        result_roll_sum = df.rolling(window=window, min_periods=2).sum()
        result_roll_generic = df.rolling(window=window, min_periods=2).apply(
            sum, raw=raw
        )
        tm.assert_frame_equal(result_roll_sum, expected)
        tm.assert_frame_equal(result_roll_generic, expected)

    @pytest.mark.parametrize("method", ["std", "mean", "sum", "max", "min", "var"])
    def test_numpy_compat(self, method):
        # see gh-12811
        r = rwindow.Rolling(Series([2, 4, 6]), window=2)

        msg = "numpy operations are not valid with window objects"

        with pytest.raises(UnsupportedFunctionCall, match=msg):
            getattr(r, method)(1, 2, 3)
        with pytest.raises(UnsupportedFunctionCall, match=msg):
            getattr(r, method)(dtype=np.float64)

    def test_closed(self):
        df = DataFrame({"A": [0, 1, 2, 3, 4]})
        # closed only allowed for datetimelike
        with pytest.raises(ValueError):
            df.rolling(window=3, closed="neither")

    @pytest.mark.parametrize("closed", ["neither", "left"])
    def test_closed_empty(self, closed, arithmetic_win_operators):
        # GH 26005
        func_name = arithmetic_win_operators
        ser = pd.Series(
            data=np.arange(5), index=pd.date_range("2000", periods=5, freq="2D")
        )
        roll = ser.rolling("1D", closed=closed)

        result = getattr(roll, func_name)()
        expected = pd.Series([np.nan] * 5, index=ser.index)
        tm.assert_series_equal(result, expected)

    @pytest.mark.parametrize("func", ["min", "max"])
    def test_closed_one_entry(self, func):
        # GH24718
        ser = pd.Series(data=[2], index=pd.date_range("2000", periods=1))
        result = getattr(ser.rolling("10D", closed="left"), func)()
        tm.assert_series_equal(result, pd.Series([np.nan], index=ser.index))

    @pytest.mark.parametrize("func", ["min", "max"])
    def test_closed_one_entry_groupby(self, func):
        # GH24718
        ser = pd.DataFrame(
            data={"A": [1, 1, 2], "B": [3, 2, 1]},
            index=pd.date_range("2000", periods=3),
        )
        result = getattr(
            ser.groupby("A", sort=False)["B"].rolling("10D", closed="left"), func
        )()
        exp_idx = pd.MultiIndex.from_arrays(
            arrays=[[1, 1, 2], ser.index], names=("A", None)
        )
        expected = pd.Series(data=[np.nan, 3, np.nan], index=exp_idx, name="B")
        tm.assert_series_equal(result, expected)

    @pytest.mark.parametrize("input_dtype", ["int", "float"])
    @pytest.mark.parametrize(
        "func,closed,expected",
        [
            ("min", "right", [0.0, 0, 0, 1, 2, 3, 4, 5, 6, 7]),
            ("min", "both", [0.0, 0, 0, 0, 1, 2, 3, 4, 5, 6]),
            ("min", "neither", [np.nan, 0, 0, 1, 2, 3, 4, 5, 6, 7]),
            ("min", "left", [np.nan, 0, 0, 0, 1, 2, 3, 4, 5, 6]),
            ("max", "right", [0.0, 1, 2, 3, 4, 5, 6, 7, 8, 9]),
            ("max", "both", [0.0, 1, 2, 3, 4, 5, 6, 7, 8, 9]),
            ("max", "neither", [np.nan, 0, 1, 2, 3, 4, 5, 6, 7, 8]),
            ("max", "left", [np.nan, 0, 1, 2, 3, 4, 5, 6, 7, 8]),
        ],
    )
    def test_closed_min_max_datetime(self, input_dtype, func, closed, expected):
        # see gh-21704
        ser = pd.Series(
            data=np.arange(10).astype(input_dtype),
            index=pd.date_range("2000", periods=10),
        )

        result = getattr(ser.rolling("3D", closed=closed), func)()
        expected = pd.Series(expected, index=ser.index)
        tm.assert_series_equal(result, expected)

    def test_closed_uneven(self):
        # see gh-21704
        ser = pd.Series(data=np.arange(10), index=pd.date_range("2000", periods=10))

        # uneven
        ser = ser.drop(index=ser.index[[1, 5]])
        result = ser.rolling("3D", closed="left").min()
        expected = pd.Series([np.nan, 0, 0, 2, 3, 4, 6, 6], index=ser.index)
        tm.assert_series_equal(result, expected)

    @pytest.mark.parametrize(
        "func,closed,expected",
        [
            ("min", "right", [np.nan, 0, 0, 1, 2, 3, 4, 5, np.nan, np.nan]),
            ("min", "both", [np.nan, 0, 0, 0, 1, 2, 3, 4, 5, np.nan]),
            ("min", "neither", [np.nan, np.nan, 0, 1, 2, 3, 4, 5, np.nan, np.nan]),
            ("min", "left", [np.nan, np.nan, 0, 0, 1, 2, 3, 4, 5, np.nan]),
            ("max", "right", [np.nan, 1, 2, 3, 4, 5, 6, 6, np.nan, np.nan]),
            ("max", "both", [np.nan, 1, 2, 3, 4, 5, 6, 6, 6, np.nan]),
            ("max", "neither", [np.nan, np.nan, 1, 2, 3, 4, 5, 6, np.nan, np.nan]),
            ("max", "left", [np.nan, np.nan, 1, 2, 3, 4, 5, 6, 6, np.nan]),
        ],
    )
    def test_closed_min_max_minp(self, func, closed, expected):
        # see gh-21704
        ser = pd.Series(data=np.arange(10), index=pd.date_range("2000", periods=10))
        ser[ser.index[-3:]] = np.nan
        result = getattr(ser.rolling("3D", min_periods=2, closed=closed), func)()
        expected = pd.Series(expected, index=ser.index)
        tm.assert_series_equal(result, expected)

    @pytest.mark.parametrize(
        "closed,expected",
        [
            ("right", [0, 0.5, 1, 2, 3, 4, 5, 6, 7, 8]),
            ("both", [0, 0.5, 1, 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5]),
            ("neither", [np.nan, 0, 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5]),
            ("left", [np.nan, 0, 0.5, 1, 2, 3, 4, 5, 6, 7]),
        ],
    )
    def test_closed_median_quantile(self, closed, expected):
        # GH 26005
        ser = pd.Series(data=np.arange(10), index=pd.date_range("2000", periods=10))
        roll = ser.rolling("3D", closed=closed)
        expected = pd.Series(expected, index=ser.index)

        result = roll.median()
        tm.assert_series_equal(result, expected)

        result = roll.quantile(0.5)
        tm.assert_series_equal(result, expected)

    @pytest.mark.parametrize("roller", ["1s", 1])
    def tests_empty_df_rolling(self, roller):
        # GH 15819 Verifies that datetime and integer rolling windows can be
        # applied to empty DataFrames
        expected = DataFrame()
        result = DataFrame().rolling(roller).sum()
        tm.assert_frame_equal(result, expected)

        # Verifies that datetime and integer rolling windows can be applied to
        # empty DataFrames with datetime index
        expected = DataFrame(index=pd.DatetimeIndex([]))
        result = DataFrame(index=pd.DatetimeIndex([])).rolling(roller).sum()
        tm.assert_frame_equal(result, expected)

    def test_empty_window_median_quantile(self):
        # GH 26005
        expected = pd.Series([np.nan, np.nan, np.nan])
        roll = pd.Series(np.arange(3)).rolling(0)

        result = roll.median()
        tm.assert_series_equal(result, expected)

        result = roll.quantile(0.1)
        tm.assert_series_equal(result, expected)

    def test_missing_minp_zero(self):
        # https://github.com/pandas-dev/pandas/pull/18921
        # minp=0
        x = pd.Series([np.nan])
        result = x.rolling(1, min_periods=0).sum()
        expected = pd.Series([0.0])
        tm.assert_series_equal(result, expected)

        # minp=1
        result = x.rolling(1, min_periods=1).sum()
        expected = pd.Series([np.nan])
        tm.assert_series_equal(result, expected)

    def test_missing_minp_zero_variable(self):
        # https://github.com/pandas-dev/pandas/pull/18921
        x = pd.Series(
            [np.nan] * 4,
            index=pd.DatetimeIndex(
                ["2017-01-01", "2017-01-04", "2017-01-06", "2017-01-07"]
            ),
        )
        result = x.rolling(pd.Timedelta("2d"), min_periods=0).sum()
        expected = pd.Series(0.0, index=x.index)
        tm.assert_series_equal(result, expected)

    def test_multi_index_names(self):

        # GH 16789, 16825
        cols = pd.MultiIndex.from_product(
            [["A", "B"], ["C", "D", "E"]], names=["1", "2"]
        )
        df = DataFrame(np.ones((10, 6)), columns=cols)
        result = df.rolling(3).cov()

        tm.assert_index_equal(result.columns, df.columns)
        assert result.index.names == [None, "1", "2"]

    @pytest.mark.parametrize("klass", [pd.Series, pd.DataFrame])
    def test_iter_raises(self, klass):
        # https://github.com/pandas-dev/pandas/issues/11704
        # Iteration over a Window
        obj = klass([1, 2, 3, 4])
        with pytest.raises(NotImplementedError):
            iter(obj.rolling(2))

    def test_rolling_axis_sum(self, axis_frame):
        # see gh-23372.
        df = DataFrame(np.ones((10, 20)))
        axis = df._get_axis_number(axis_frame)

        if axis == 0:
            expected = DataFrame({i: [np.nan] * 2 + [3.0] * 8 for i in range(20)})
        else:
            # axis == 1
            expected = DataFrame([[np.nan] * 2 + [3.0] * 18] * 10)

        result = df.rolling(3, axis=axis_frame).sum()
        tm.assert_frame_equal(result, expected)

    def test_rolling_axis_count(self, axis_frame):
        # see gh-26055
        df = DataFrame({"x": range(3), "y": range(3)})

        axis = df._get_axis_number(axis_frame)

        if axis in [0, "index"]:
            expected = DataFrame({"x": [1.0, 2.0, 2.0], "y": [1.0, 2.0, 2.0]})
        else:
            expected = DataFrame({"x": [1.0, 1.0, 1.0], "y": [2.0, 2.0, 2.0]})

        result = df.rolling(2, axis=axis_frame).count()
        tm.assert_frame_equal(result, expected)


class TestExpanding(Base):
    def setup_method(self, method):
        self._create_data()

    def test_doc_string(self):

        df = DataFrame({"B": [0, 1, 2, np.nan, 4]})
        df
        df.expanding(2).sum()

    @pytest.mark.parametrize("which", ["series", "frame"])
    def test_constructor(self, which):
        # GH 12669

        o = getattr(self, which)
        c = o.expanding

        # valid
        c(min_periods=1)
        c(min_periods=1, center=True)
        c(min_periods=1, center=False)

        # not valid
        for w in [2.0, "foo", np.array([2])]:
            with pytest.raises(ValueError):
                c(min_periods=w)
            with pytest.raises(ValueError):
                c(min_periods=1, center=w)

    @pytest.mark.parametrize("method", ["std", "mean", "sum", "max", "min", "var"])
    def test_numpy_compat(self, method):
        # see gh-12811
        e = rwindow.Expanding(Series([2, 4, 6]), window=2)

        msg = "numpy operations are not valid with window objects"

        with pytest.raises(UnsupportedFunctionCall, match=msg):
            getattr(e, method)(1, 2, 3)
        with pytest.raises(UnsupportedFunctionCall, match=msg):
            getattr(e, method)(dtype=np.float64)

    @pytest.mark.parametrize(
        "expander",
        [
            1,
            pytest.param(
                "ls",
                marks=pytest.mark.xfail(
                    reason="GH#16425 expanding with offset not supported"
                ),
            ),
        ],
    )
    def test_empty_df_expanding(self, expander):
        # GH 15819 Verifies that datetime and integer expanding windows can be
        # applied to empty DataFrames

        expected = DataFrame()
        result = DataFrame().expanding(expander).sum()
        tm.assert_frame_equal(result, expected)

        # Verifies that datetime and integer expanding windows can be applied
        # to empty DataFrames with datetime index
        expected = DataFrame(index=pd.DatetimeIndex([]))
        result = DataFrame(index=pd.DatetimeIndex([])).expanding(expander).sum()
        tm.assert_frame_equal(result, expected)

    def test_missing_minp_zero(self):
        # https://github.com/pandas-dev/pandas/pull/18921
        # minp=0
        x = pd.Series([np.nan])
        result = x.expanding(min_periods=0).sum()
        expected = pd.Series([0.0])
        tm.assert_series_equal(result, expected)

        # minp=1
        result = x.expanding(min_periods=1).sum()
        expected = pd.Series([np.nan])
        tm.assert_series_equal(result, expected)

    @pytest.mark.parametrize("klass", [pd.Series, pd.DataFrame])
    def test_iter_raises(self, klass):
        # https://github.com/pandas-dev/pandas/issues/11704
        # Iteration over a Window
        obj = klass([1, 2, 3, 4])
        with pytest.raises(NotImplementedError):
            iter(obj.expanding(2))

    def test_expanding_axis(self, axis_frame):
        # see gh-23372.
        df = DataFrame(np.ones((10, 20)))
        axis = df._get_axis_number(axis_frame)

        if axis == 0:
            expected = DataFrame(
                {i: [np.nan] * 2 + [float(j) for j in range(3, 11)] for i in range(20)}
            )
        else:
            # axis == 1
            expected = DataFrame([[np.nan] * 2 + [float(i) for i in range(3, 21)]] * 10)

        result = df.expanding(3, axis=axis_frame).sum()
        tm.assert_frame_equal(result, expected)


class TestEWM(Base):
    def setup_method(self, method):
        self._create_data()

    def test_doc_string(self):

        df = DataFrame({"B": [0, 1, 2, np.nan, 4]})
        df
        df.ewm(com=0.5).mean()

    @pytest.mark.parametrize("which", ["series", "frame"])
    def test_constructor(self, which):
        o = getattr(self, which)
        c = o.ewm

        # valid
        c(com=0.5)
        c(span=1.5)
        c(alpha=0.5)
        c(halflife=0.75)
        c(com=0.5, span=None)
        c(alpha=0.5, com=None)
        c(halflife=0.75, alpha=None)

        # not valid: mutually exclusive
        with pytest.raises(ValueError):
            c(com=0.5, alpha=0.5)
        with pytest.raises(ValueError):
            c(span=1.5, halflife=0.75)
        with pytest.raises(ValueError):
            c(alpha=0.5, span=1.5)

        # not valid: com < 0
        with pytest.raises(ValueError):
            c(com=-0.5)

        # not valid: span < 1
        with pytest.raises(ValueError):
            c(span=0.5)

        # not valid: halflife <= 0
        with pytest.raises(ValueError):
            c(halflife=0)

        # not valid: alpha <= 0 or alpha > 1
        for alpha in (-0.5, 1.5):
            with pytest.raises(ValueError):
                c(alpha=alpha)

    @pytest.mark.parametrize("method", ["std", "mean", "var"])
    def test_numpy_compat(self, method):
        # see gh-12811
        e = rwindow.EWM(Series([2, 4, 6]), alpha=0.5)

        msg = "numpy operations are not valid with window objects"

        with pytest.raises(UnsupportedFunctionCall, match=msg):
            getattr(e, method)(1, 2, 3)
        with pytest.raises(UnsupportedFunctionCall, match=msg):
            getattr(e, method)(dtype=np.float64)

    def test_agg_unknown(self):
        df = pd.DataFrame({"A": np.arange(5)})
        roll = df.rolling(2)

        msg = "'foo' is an unknown string function"
        with pytest.raises(AttributeError, match=msg):
            roll.agg("foo")

        with pytest.raises(AttributeError, match=msg):
            roll.agg(["foo"])

        with pytest.raises(AttributeError, match=msg):
            roll.agg({"A": "foo"})


# gh-12373 : rolling functions error on float32 data
# make sure rolling functions works for different dtypes
#
# NOTE that these are yielded tests and so _create_data
# is explicitly called.
#
# further note that we are only checking rolling for fully dtype
# compliance (though both expanding and ewm inherit)
class Dtype:
    window = 2

    funcs = {
        "count": lambda v: v.count(),
        "max": lambda v: v.max(),
        "min": lambda v: v.min(),
        "sum": lambda v: v.sum(),
        "mean": lambda v: v.mean(),
        "std": lambda v: v.std(),
        "var": lambda v: v.var(),
        "median": lambda v: v.median(),
    }

    def get_expects(self):
        expects = {
            "sr1": {
                "count": Series([1, 2, 2, 2, 2], dtype="float64"),
                "max": Series([np.nan, 1, 2, 3, 4], dtype="float64"),
                "min": Series([np.nan, 0, 1, 2, 3], dtype="float64"),
                "sum": Series([np.nan, 1, 3, 5, 7], dtype="float64"),
                "mean": Series([np.nan, 0.5, 1.5, 2.5, 3.5], dtype="float64"),
                "std": Series([np.nan] + [np.sqrt(0.5)] * 4, dtype="float64"),
                "var": Series([np.nan, 0.5, 0.5, 0.5, 0.5], dtype="float64"),
                "median": Series([np.nan, 0.5, 1.5, 2.5, 3.5], dtype="float64"),
            },
            "sr2": {
                "count": Series([1, 2, 2, 2, 2], dtype="float64"),
                "max": Series([np.nan, 10, 8, 6, 4], dtype="float64"),
                "min": Series([np.nan, 8, 6, 4, 2], dtype="float64"),
                "sum": Series([np.nan, 18, 14, 10, 6], dtype="float64"),
                "mean": Series([np.nan, 9, 7, 5, 3], dtype="float64"),
                "std": Series([np.nan] + [np.sqrt(2)] * 4, dtype="float64"),
                "var": Series([np.nan, 2, 2, 2, 2], dtype="float64"),
                "median": Series([np.nan, 9, 7, 5, 3], dtype="float64"),
            },
            "df": {
                "count": DataFrame(
                    {0: Series([1, 2, 2, 2, 2]), 1: Series([1, 2, 2, 2, 2])},
                    dtype="float64",
                ),
                "max": DataFrame(
                    {0: Series([np.nan, 2, 4, 6, 8]), 1: Series([np.nan, 3, 5, 7, 9])},
                    dtype="float64",
                ),
                "min": DataFrame(
                    {0: Series([np.nan, 0, 2, 4, 6]), 1: Series([np.nan, 1, 3, 5, 7])},
                    dtype="float64",
                ),
                "sum": DataFrame(
                    {
                        0: Series([np.nan, 2, 6, 10, 14]),
                        1: Series([np.nan, 4, 8, 12, 16]),
                    },
                    dtype="float64",
                ),
                "mean": DataFrame(
                    {0: Series([np.nan, 1, 3, 5, 7]), 1: Series([np.nan, 2, 4, 6, 8])},
                    dtype="float64",
                ),
                "std": DataFrame(
                    {
                        0: Series([np.nan] + [np.sqrt(2)] * 4),
                        1: Series([np.nan] + [np.sqrt(2)] * 4),
                    },
                    dtype="float64",
                ),
                "var": DataFrame(
                    {0: Series([np.nan, 2, 2, 2, 2]), 1: Series([np.nan, 2, 2, 2, 2])},
                    dtype="float64",
                ),
                "median": DataFrame(
                    {0: Series([np.nan, 1, 3, 5, 7]), 1: Series([np.nan, 2, 4, 6, 8])},
                    dtype="float64",
                ),
            },
        }
        return expects

    def _create_dtype_data(self, dtype):
        sr1 = Series(np.arange(5), dtype=dtype)
        sr2 = Series(np.arange(10, 0, -2), dtype=dtype)
        df = DataFrame(np.arange(10).reshape((5, 2)), dtype=dtype)

        data = {"sr1": sr1, "sr2": sr2, "df": df}

        return data

    def _create_data(self):
        self.data = self._create_dtype_data(self.dtype)
        self.expects = self.get_expects()

    def test_dtypes(self):
        self._create_data()
        for f_name, d_name in product(self.funcs.keys(), self.data.keys()):

            f = self.funcs[f_name]
            d = self.data[d_name]
            exp = self.expects[d_name][f_name]
            self.check_dtypes(f, f_name, d, d_name, exp)

    def check_dtypes(self, f, f_name, d, d_name, exp):
        roll = d.rolling(window=self.window)
        result = f(roll)
        tm.assert_almost_equal(result, exp)


class TestDtype_object(Dtype):
    dtype = object


class Dtype_integer(Dtype):
    pass


class TestDtype_int8(Dtype_integer):
    dtype = np.int8


class TestDtype_int16(Dtype_integer):
    dtype = np.int16


class TestDtype_int32(Dtype_integer):
    dtype = np.int32


class TestDtype_int64(Dtype_integer):
    dtype = np.int64


class Dtype_uinteger(Dtype):
    pass


class TestDtype_uint8(Dtype_uinteger):
    dtype = np.uint8


class TestDtype_uint16(Dtype_uinteger):
    dtype = np.uint16


class TestDtype_uint32(Dtype_uinteger):
    dtype = np.uint32


class TestDtype_uint64(Dtype_uinteger):
    dtype = np.uint64


class Dtype_float(Dtype):
    pass


class TestDtype_float16(Dtype_float):
    dtype = np.float16


class TestDtype_float32(Dtype_float):
    dtype = np.float32


class TestDtype_float64(Dtype_float):
    dtype = np.float64


class TestDtype_category(Dtype):
    dtype = "category"
    include_df = False

    def _create_dtype_data(self, dtype):
        sr1 = Series(range(5), dtype=dtype)
        sr2 = Series(range(10, 0, -2), dtype=dtype)

        data = {"sr1": sr1, "sr2": sr2}

        return data


class DatetimeLike(Dtype):
    def check_dtypes(self, f, f_name, d, d_name, exp):

        roll = d.rolling(window=self.window)
        if f_name == "count":
            result = f(roll)
            tm.assert_almost_equal(result, exp)

        else:
            with pytest.raises(DataError):
                f(roll)


class TestDtype_timedelta(DatetimeLike):
    dtype = np.dtype("m8[ns]")


class TestDtype_datetime(DatetimeLike):
    dtype = np.dtype("M8[ns]")


class TestDtype_datetime64UTC(DatetimeLike):
    dtype = "datetime64[ns, UTC]"

    def _create_data(self):
        pytest.skip(
            "direct creation of extension dtype "
            "datetime64[ns, UTC] is not supported ATM"
        )


@pytest.mark.filterwarnings("ignore:can't resolve package:ImportWarning")
class TestMoments(Base):
    def setup_method(self, method):
        self._create_data()

    def test_centered_axis_validation(self):

        # ok
        Series(np.ones(10)).rolling(window=3, center=True, axis=0).mean()

        # bad axis
        with pytest.raises(ValueError):
            Series(np.ones(10)).rolling(window=3, center=True, axis=1).mean()

        # ok ok
        DataFrame(np.ones((10, 10))).rolling(window=3, center=True, axis=0).mean()
        DataFrame(np.ones((10, 10))).rolling(window=3, center=True, axis=1).mean()

        # bad axis
        with pytest.raises(ValueError):
            (DataFrame(np.ones((10, 10))).rolling(window=3, center=True, axis=2).mean())

    def test_rolling_sum(self):
        self._check_moment_func(np.nansum, name="sum", zero_min_periods_equal=False)

    def test_rolling_count(self):
        counter = lambda x: np.isfinite(x).astype(float).sum()
        self._check_moment_func(
            counter, name="count", has_min_periods=False, fill_value=0
        )

    def test_rolling_mean(self):
        self._check_moment_func(np.mean, name="mean")

    @td.skip_if_no_scipy
    def test_cmov_mean(self):
        # GH 8238
        vals = np.array(
            [6.95, 15.21, 4.72, 9.12, 13.81, 13.49, 16.68, 9.48, 10.63, 14.48]
        )
        result = Series(vals).rolling(5, center=True).mean()
        expected = Series(
            [
                np.nan,
                np.nan,
                9.962,
                11.27,
                11.564,
                12.516,
                12.818,
                12.952,
                np.nan,
                np.nan,
            ]
        )
        tm.assert_series_equal(expected, result)

    @td.skip_if_no_scipy
    def test_cmov_window(self):
        # GH 8238
        vals = np.array(
            [6.95, 15.21, 4.72, 9.12, 13.81, 13.49, 16.68, 9.48, 10.63, 14.48]
        )
        result = Series(vals).rolling(5, win_type="boxcar", center=True).mean()
        expected = Series(
            [
                np.nan,
                np.nan,
                9.962,
                11.27,
                11.564,
                12.516,
                12.818,
                12.952,
                np.nan,
                np.nan,
            ]
        )
        tm.assert_series_equal(expected, result)

    @td.skip_if_no_scipy
    def test_cmov_window_corner(self):
        # GH 8238
        # all nan
        vals = pd.Series([np.nan] * 10)
        result = vals.rolling(5, center=True, win_type="boxcar").mean()
        assert np.isnan(result).all()

        # empty
        vals = pd.Series([])
        result = vals.rolling(5, center=True, win_type="boxcar").mean()
        assert len(result) == 0

        # shorter than window
        vals = pd.Series(np.random.randn(5))
        result = vals.rolling(10, win_type="boxcar").mean()
        assert np.isnan(result).all()
        assert len(result) == 5

    @td.skip_if_no_scipy
    def test_cmov_window_frame(self):
        # Gh 8238
        vals = np.array(
            [
                [12.18, 3.64],
                [10.18, 9.16],
                [13.24, 14.61],
                [4.51, 8.11],
                [6.15, 11.44],
                [9.14, 6.21],
                [11.31, 10.67],
                [2.94, 6.51],
                [9.42, 8.39],
                [12.44, 7.34],
            ]
        )

        xp = np.array(
            [
                [np.nan, np.nan],
                [np.nan, np.nan],
                [9.252, 9.392],
                [8.644, 9.906],
                [8.87, 10.208],
                [6.81, 8.588],
                [7.792, 8.644],
                [9.05, 7.824],
                [np.nan, np.nan],
                [np.nan, np.nan],
            ]
        )

        # DataFrame
        rs = DataFrame(vals).rolling(5, win_type="boxcar", center=True).mean()
        tm.assert_frame_equal(DataFrame(xp), rs)

        # invalid method
        with pytest.raises(AttributeError):
            (DataFrame(vals).rolling(5, win_type="boxcar", center=True).std())

        # sum
        xp = np.array(
            [
                [np.nan, np.nan],
                [np.nan, np.nan],
                [46.26, 46.96],
                [43.22, 49.53],
                [44.35, 51.04],
                [34.05, 42.94],
                [38.96, 43.22],
                [45.25, 39.12],
                [np.nan, np.nan],
                [np.nan, np.nan],
            ]
        )

        rs = DataFrame(vals).rolling(5, win_type="boxcar", center=True).sum()
        tm.assert_frame_equal(DataFrame(xp), rs)

    @td.skip_if_no_scipy
    def test_cmov_window_na_min_periods(self):
        # min_periods
        vals = Series(np.random.randn(10))
        vals[4] = np.nan
        vals[8] = np.nan

        xp = vals.rolling(5, min_periods=4, center=True).mean()
        rs = vals.rolling(5, win_type="boxcar", min_periods=4, center=True).mean()
        tm.assert_series_equal(xp, rs)

    @td.skip_if_no_scipy
    def test_cmov_window_regular(self, win_types):
        # GH 8238
        vals = np.array(
            [6.95, 15.21, 4.72, 9.12, 13.81, 13.49, 16.68, 9.48, 10.63, 14.48]
        )
        xps = {
            "hamming": [
                np.nan,
                np.nan,
                8.71384,
                9.56348,
                12.38009,
                14.03687,
                13.8567,
                11.81473,
                np.nan,
                np.nan,
            ],
            "triang": [
                np.nan,
                np.nan,
                9.28667,
                10.34667,
                12.00556,
                13.33889,
                13.38,
                12.33667,
                np.nan,
                np.nan,
            ],
            "barthann": [
                np.nan,
                np.nan,
                8.4425,
                9.1925,
                12.5575,
                14.3675,
                14.0825,
                11.5675,
                np.nan,
                np.nan,
            ],
            "bohman": [
                np.nan,
                np.nan,
                7.61599,
                9.1764,
                12.83559,
                14.17267,
                14.65923,
                11.10401,
                np.nan,
                np.nan,
            ],
            "blackmanharris": [
                np.nan,
                np.nan,
                6.97691,
                9.16438,
                13.05052,
                14.02156,
                15.10512,
                10.74574,
                np.nan,
                np.nan,
            ],
            "nuttall": [
                np.nan,
                np.nan,
                7.04618,
                9.16786,
                13.02671,
                14.03559,
                15.05657,
                10.78514,
                np.nan,
                np.nan,
            ],
            "blackman": [
                np.nan,
                np.nan,
                7.73345,
                9.17869,
                12.79607,
                14.20036,
                14.57726,
                11.16988,
                np.nan,
                np.nan,
            ],
            "bartlett": [
                np.nan,
                np.nan,
                8.4425,
                9.1925,
                12.5575,
                14.3675,
                14.0825,
                11.5675,
                np.nan,
                np.nan,
            ],
        }

        xp = Series(xps[win_types])
        rs = Series(vals).rolling(5, win_type=win_types, center=True).mean()
        tm.assert_series_equal(xp, rs)

    @td.skip_if_no_scipy
    def test_cmov_window_regular_linear_range(self, win_types):
        # GH 8238
        vals = np.array(range(10), dtype=np.float)
        xp = vals.copy()
        xp[:2] = np.nan
        xp[-2:] = np.nan
        xp = Series(xp)

        rs = Series(vals).rolling(5, win_type=win_types, center=True).mean()
        tm.assert_series_equal(xp, rs)

    @td.skip_if_no_scipy
    def test_cmov_window_regular_missing_data(self, win_types):
        # GH 8238
        vals = np.array(
            [6.95, 15.21, 4.72, 9.12, 13.81, 13.49, 16.68, np.nan, 10.63, 14.48]
        )
        xps = {
            "bartlett": [
                np.nan,
                np.nan,
                9.70333,
                10.5225,
                8.4425,
                9.1925,
                12.5575,
                14.3675,
                15.61667,
                13.655,
            ],
            "blackman": [
                np.nan,
                np.nan,
                9.04582,
                11.41536,
                7.73345,
                9.17869,
                12.79607,
                14.20036,
                15.8706,
                13.655,
            ],
            "barthann": [
                np.nan,
                np.nan,
                9.70333,
                10.5225,
                8.4425,
                9.1925,
                12.5575,
                14.3675,
                15.61667,
                13.655,
            ],
            "bohman": [
                np.nan,
                np.nan,
                8.9444,
                11.56327,
                7.61599,
                9.1764,
                12.83559,
                14.17267,
                15.90976,
                13.655,
            ],
            "hamming": [
                np.nan,
                np.nan,
                9.59321,
                10.29694,
                8.71384,
                9.56348,
                12.38009,
                14.20565,
                15.24694,
                13.69758,
            ],
            "nuttall": [
                np.nan,
                np.nan,
                8.47693,
                12.2821,
                7.04618,
                9.16786,
                13.02671,
                14.03673,
                16.08759,
                13.65553,
            ],
            "triang": [
                np.nan,
                np.nan,
                9.33167,
                9.76125,
                9.28667,
                10.34667,
                12.00556,
                13.82125,
                14.49429,
                13.765,
            ],
            "blackmanharris": [
                np.nan,
                np.nan,
                8.42526,
                12.36824,
                6.97691,
                9.16438,
                13.05052,
                14.02175,
                16.1098,
                13.65509,
            ],
        }

        xp = Series(xps[win_types])
        rs = Series(vals).rolling(5, win_type=win_types, min_periods=3).mean()
        tm.assert_series_equal(xp, rs)

    @td.skip_if_no_scipy
    def test_cmov_window_special(self, win_types_special):
        # GH 8238
        kwds = {
            "kaiser": {"beta": 1.0},
            "gaussian": {"std": 1.0},
            "general_gaussian": {"power": 2.0, "width": 2.0},
            "exponential": {"tau": 10},
        }

        vals = np.array(
            [6.95, 15.21, 4.72, 9.12, 13.81, 13.49, 16.68, 9.48, 10.63, 14.48]
        )

        xps = {
            "gaussian": [
                np.nan,
                np.nan,
                8.97297,
                9.76077,
                12.24763,
                13.89053,
                13.65671,
                12.01002,
                np.nan,
                np.nan,
            ],
            "general_gaussian": [
                np.nan,
                np.nan,
                9.85011,
                10.71589,
                11.73161,
                13.08516,
                12.95111,
                12.74577,
                np.nan,
                np.nan,
            ],
            "kaiser": [
                np.nan,
                np.nan,
                9.86851,
                11.02969,
                11.65161,
                12.75129,
                12.90702,
                12.83757,
                np.nan,
                np.nan,
            ],
            "exponential": [
                np.nan,
                np.nan,
                9.83364,
                11.10472,
                11.64551,
                12.66138,
                12.92379,
                12.83770,
                np.nan,
                np.nan,
            ],
        }

        xp = Series(xps[win_types_special])
        rs = (
            Series(vals)
            .rolling(5, win_type=win_types_special, center=True)
            .mean(**kwds[win_types_special])
        )
        tm.assert_series_equal(xp, rs)

    @td.skip_if_no_scipy
    def test_cmov_window_special_linear_range(self, win_types_special):
        # GH 8238
        kwds = {
            "kaiser": {"beta": 1.0},
            "gaussian": {"std": 1.0},
            "general_gaussian": {"power": 2.0, "width": 2.0},
            "slepian": {"width": 0.5},
            "exponential": {"tau": 10},
        }

        vals = np.array(range(10), dtype=np.float)
        xp = vals.copy()
        xp[:2] = np.nan
        xp[-2:] = np.nan
        xp = Series(xp)

        rs = (
            Series(vals)
            .rolling(5, win_type=win_types_special, center=True)
            .mean(**kwds[win_types_special])
        )
        tm.assert_series_equal(xp, rs)

    def test_rolling_median(self):
        self._check_moment_func(np.median, name="median")

    def test_rolling_min(self):
        self._check_moment_func(np.min, name="min")

        a = pd.Series([1, 2, 3, 4, 5])
        result = a.rolling(window=100, min_periods=1).min()
        expected = pd.Series(np.ones(len(a)))
        tm.assert_series_equal(result, expected)

        with pytest.raises(ValueError):
            pd.Series([1, 2, 3]).rolling(window=3, min_periods=5).min()

    def test_rolling_max(self):
        self._check_moment_func(np.max, name="max")

        a = pd.Series([1, 2, 3, 4, 5], dtype=np.float64)
        b = a.rolling(window=100, min_periods=1).max()
        tm.assert_almost_equal(a, b)

        with pytest.raises(ValueError):
            pd.Series([1, 2, 3]).rolling(window=3, min_periods=5).max()

    @pytest.mark.parametrize("q", [0.0, 0.1, 0.5, 0.9, 1.0])
    def test_rolling_quantile(self, q):
        def scoreatpercentile(a, per):
            values = np.sort(a, axis=0)

            idx = int(per / 1.0 * (values.shape[0] - 1))

            if idx == values.shape[0] - 1:
                retval = values[-1]

            else:
                qlow = float(idx) / float(values.shape[0] - 1)
                qhig = float(idx + 1) / float(values.shape[0] - 1)
                vlow = values[idx]
                vhig = values[idx + 1]
                retval = vlow + (vhig - vlow) * (per - qlow) / (qhig - qlow)

            return retval

        def quantile_func(x):
            return scoreatpercentile(x, q)

        self._check_moment_func(quantile_func, name="quantile", quantile=q)

    def test_rolling_quantile_np_percentile(self):
        # #9413: Tests that rolling window's quantile default behavior
        # is analogous to Numpy's percentile
        row = 10
        col = 5
        idx = pd.date_range("20100101", periods=row, freq="B")
        df = DataFrame(np.random.rand(row * col).reshape((row, -1)), index=idx)

        df_quantile = df.quantile([0.25, 0.5, 0.75], axis=0)
        np_percentile = np.percentile(df, [25, 50, 75], axis=0)

        tm.assert_almost_equal(df_quantile.values, np.array(np_percentile))

    @pytest.mark.parametrize("quantile", [0.0, 0.1, 0.45, 0.5, 1])
    @pytest.mark.parametrize(
        "interpolation", ["linear", "lower", "higher", "nearest", "midpoint"]
    )
    @pytest.mark.parametrize(
        "data",
        [
            [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0],
            [8.0, 1.0, 3.0, 4.0, 5.0, 2.0, 6.0, 7.0],
            [0.0, np.nan, 0.2, np.nan, 0.4],
            [np.nan, np.nan, np.nan, np.nan],
            [np.nan, 0.1, np.nan, 0.3, 0.4, 0.5],
            [0.5],
            [np.nan, 0.7, 0.6],
        ],
    )
    def test_rolling_quantile_interpolation_options(
        self, quantile, interpolation, data
    ):
        # Tests that rolling window's quantile behavior is analogous to
        # Series' quantile for each interpolation option
        s = Series(data)

        q1 = s.quantile(quantile, interpolation)
        q2 = s.expanding(min_periods=1).quantile(quantile, interpolation).iloc[-1]

        if np.isnan(q1):
            assert np.isnan(q2)
        else:
            assert q1 == q2

    def test_invalid_quantile_value(self):
        data = np.arange(5)
        s = Series(data)

        msg = "Interpolation 'invalid' is not supported"
        with pytest.raises(ValueError, match=msg):
            s.rolling(len(data), min_periods=1).quantile(0.5, interpolation="invalid")

    def test_rolling_quantile_param(self):
        ser = Series([0.0, 0.1, 0.5, 0.9, 1.0])

        with pytest.raises(ValueError):
            ser.rolling(3).quantile(-0.1)

        with pytest.raises(ValueError):
            ser.rolling(3).quantile(10.0)

        with pytest.raises(TypeError):
            ser.rolling(3).quantile("foo")

    def test_rolling_apply(self, raw):
        # suppress warnings about empty slices, as we are deliberately testing
        # with a 0-length Series

        with warnings.catch_warnings():
            warnings.filterwarnings(
                "ignore",
                message=".*(empty slice|0 for slice).*",
                category=RuntimeWarning,
            )

            def f(x):
                return x[np.isfinite(x)].mean()

            self._check_moment_func(np.mean, name="apply", func=f, raw=raw)

            expected = Series([])
            result = expected.rolling(10).apply(lambda x: x.mean(), raw=raw)
            tm.assert_series_equal(result, expected)

        # gh-8080
        s = Series([None, None, None])
        result = s.rolling(2, min_periods=0).apply(lambda x: len(x), raw=raw)
        expected = Series([1.0, 2.0, 2.0])
        tm.assert_series_equal(result, expected)

        result = s.rolling(2, min_periods=0).apply(len, raw=raw)
        tm.assert_series_equal(result, expected)

    @pytest.mark.parametrize("klass", [Series, DataFrame])
    @pytest.mark.parametrize(
        "method", [lambda x: x.rolling(window=2), lambda x: x.expanding()]
    )
    def test_apply_future_warning(self, klass, method):

        # gh-5071
        s = klass(np.arange(3))

        with tm.assert_produces_warning(FutureWarning):
            method(s).apply(lambda x: len(x))

    def test_rolling_apply_out_of_bounds(self, raw):
        # gh-1850
        vals = pd.Series([1, 2, 3, 4])

        result = vals.rolling(10).apply(np.sum, raw=raw)
        assert result.isna().all()

        result = vals.rolling(10, min_periods=1).apply(np.sum, raw=raw)
        expected = pd.Series([1, 3, 6, 10], dtype=float)
        tm.assert_almost_equal(result, expected)

    @pytest.mark.parametrize("window", [2, "2s"])
    def test_rolling_apply_with_pandas_objects(self, window):
        # 5071
        df = pd.DataFrame(
            {"A": np.random.randn(5), "B": np.random.randint(0, 10, size=5)},
            index=pd.date_range("20130101", periods=5, freq="s"),
        )

        # we have an equal spaced timeseries index
        # so simulate removing the first period
        def f(x):
            if x.index[0] == df.index[0]:
                return np.nan
            return x.iloc[-1]

        result = df.rolling(window).apply(f, raw=False)
        expected = df.iloc[2:].reindex_like(df)
        tm.assert_frame_equal(result, expected)

        with pytest.raises(AttributeError):
            df.rolling(window).apply(f, raw=True)

    def test_rolling_std(self):
        self._check_moment_func(lambda x: np.std(x, ddof=1), name="std")
        self._check_moment_func(lambda x: np.std(x, ddof=0), name="std", ddof=0)

    def test_rolling_std_1obs(self):
        vals = pd.Series([1.0, 2.0, 3.0, 4.0, 5.0])

        result = vals.rolling(1, min_periods=1).std()
        expected = pd.Series([np.nan] * 5)
        tm.assert_series_equal(result, expected)

        result = vals.rolling(1, min_periods=1).std(ddof=0)
        expected = pd.Series([0.0] * 5)
        tm.assert_series_equal(result, expected)

        result = pd.Series([np.nan, np.nan, 3, 4, 5]).rolling(3, min_periods=2).std()
        assert np.isnan(result[2])

    def test_rolling_std_neg_sqrt(self):
        # unit test from Bottleneck

        # Test move_nanstd for neg sqrt.

        a = pd.Series(
            [
                0.0011448196318903589,
                0.00028718669878572767,
                0.00028718669878572767,
                0.00028718669878572767,
                0.00028718669878572767,
            ]
        )
        b = a.rolling(window=3).std()
        assert np.isfinite(b[2:]).all()

        b = a.ewm(span=3).std()
        assert np.isfinite(b[2:]).all()

    def test_rolling_var(self):
        self._check_moment_func(lambda x: np.var(x, ddof=1), name="var")
        self._check_moment_func(lambda x: np.var(x, ddof=0), name="var", ddof=0)

    @td.skip_if_no_scipy
    def test_rolling_skew(self):
        from scipy.stats import skew

        self._check_moment_func(lambda x: skew(x, bias=False), name="skew")

    @td.skip_if_no_scipy
    def test_rolling_kurt(self):
        from scipy.stats import kurtosis

        self._check_moment_func(lambda x: kurtosis(x, bias=False), name="kurt")

    def _check_moment_func(
        self,
        static_comp,
        name,
        has_min_periods=True,
        has_center=True,
        has_time_rule=True,
        fill_value=None,
        zero_min_periods_equal=True,
        **kwargs
    ):
        def get_result(obj, window, min_periods=None, center=False):
            r = obj.rolling(window=window, min_periods=min_periods, center=center)
            return getattr(r, name)(**kwargs)

        series_result = get_result(self.series, window=50)
        assert isinstance(series_result, Series)
        tm.assert_almost_equal(series_result.iloc[-1], static_comp(self.series[-50:]))

        frame_result = get_result(self.frame, window=50)
        assert isinstance(frame_result, DataFrame)
        tm.assert_series_equal(
            frame_result.iloc[-1, :],
            self.frame.iloc[-50:, :].apply(static_comp, axis=0, raw=raw),
            check_names=False,
        )

        # check time_rule works
        if has_time_rule:
            win = 25
            minp = 10
            series = self.series[::2].resample("B").mean()
            frame = self.frame[::2].resample("B").mean()

            if has_min_periods:
                series_result = get_result(series, window=win, min_periods=minp)
                frame_result = get_result(frame, window=win, min_periods=minp)
            else:
                series_result = get_result(series, window=win)
                frame_result = get_result(frame, window=win)

            last_date = series_result.index[-1]
            prev_date = last_date - 24 * offsets.BDay()

            trunc_series = self.series[::2].truncate(prev_date, last_date)
            trunc_frame = self.frame[::2].truncate(prev_date, last_date)

            tm.assert_almost_equal(series_result[-1], static_comp(trunc_series))

            tm.assert_series_equal(
                frame_result.xs(last_date),
                trunc_frame.apply(static_comp, raw=raw),
                check_names=False,
            )

        # excluding NaNs correctly
        obj = Series(randn(50))
        obj[:10] = np.NaN
        obj[-10:] = np.NaN
        if has_min_periods:
            result = get_result(obj, 50, min_periods=30)
            tm.assert_almost_equal(result.iloc[-1], static_comp(obj[10:-10]))

            # min_periods is working correctly
            result = get_result(obj, 20, min_periods=15)
            assert isna(result.iloc[23])
            assert not isna(result.iloc[24])

            assert not isna(result.iloc[-6])
            assert isna(result.iloc[-5])

            obj2 = Series(randn(20))
            result = get_result(obj2, 10, min_periods=5)
            assert isna(result.iloc[3])
            assert notna(result.iloc[4])

            if zero_min_periods_equal:
                # min_periods=0 may be equivalent to min_periods=1
                result0 = get_result(obj, 20, min_periods=0)
                result1 = get_result(obj, 20, min_periods=1)
                tm.assert_almost_equal(result0, result1)
        else:
            result = get_result(obj, 50)
            tm.assert_almost_equal(result.iloc[-1], static_comp(obj[10:-10]))

        # window larger than series length (#7297)
        if has_min_periods:
            for minp in (0, len(self.series) - 1, len(self.series)):
                result = get_result(self.series, len(self.series) + 1, min_periods=minp)
                expected = get_result(self.series, len(self.series), min_periods=minp)
                nan_mask = isna(result)
                tm.assert_series_equal(nan_mask, isna(expected))

                nan_mask = ~nan_mask
                tm.assert_almost_equal(result[nan_mask], expected[nan_mask])
        else:
            result = get_result(self.series, len(self.series) + 1)
            expected = get_result(self.series, len(self.series))
            nan_mask = isna(result)
            tm.assert_series_equal(nan_mask, isna(expected))

            nan_mask = ~nan_mask
            tm.assert_almost_equal(result[nan_mask], expected[nan_mask])

        # check center=True
        if has_center:
            if has_min_periods:
                result = get_result(obj, 20, min_periods=15, center=True)
                expected = get_result(
                    pd.concat([obj, Series([np.NaN] * 9)]), 20, min_periods=15
                )[9:].reset_index(drop=True)
            else:
                result = get_result(obj, 20, center=True)
                expected = get_result(pd.concat([obj, Series([np.NaN] * 9)]), 20)[
                    9:
                ].reset_index(drop=True)

            tm.assert_series_equal(result, expected)

            # shifter index
            s = ["x%d" % x for x in range(12)]

            if has_min_periods:
                minp = 10

                series_xp = (
                    get_result(
                        self.series.reindex(list(self.series.index) + s),
                        window=25,
                        min_periods=minp,
                    )
                    .shift(-12)
                    .reindex(self.series.index)
                )
                frame_xp = (
                    get_result(
                        self.frame.reindex(list(self.frame.index) + s),
                        window=25,
                        min_periods=minp,
                    )
                    .shift(-12)
                    .reindex(self.frame.index)
                )

                series_rs = get_result(
                    self.series, window=25, min_periods=minp, center=True
                )
                frame_rs = get_result(
                    self.frame, window=25, min_periods=minp, center=True
                )

            else:
                series_xp = (
                    get_result(
                        self.series.reindex(list(self.series.index) + s), window=25
                    )
                    .shift(-12)
                    .reindex(self.series.index)
                )
                frame_xp = (
                    get_result(
                        self.frame.reindex(list(self.frame.index) + s), window=25
                    )
                    .shift(-12)
                    .reindex(self.frame.index)
                )

                series_rs = get_result(self.series, window=25, center=True)
                frame_rs = get_result(self.frame, window=25, center=True)

            if fill_value is not None:
                series_xp = series_xp.fillna(fill_value)
                frame_xp = frame_xp.fillna(fill_value)
            tm.assert_series_equal(series_xp, series_rs)
            tm.assert_frame_equal(frame_xp, frame_rs)

    def test_ewma(self):
        self._check_ew(name="mean")

        vals = pd.Series(np.zeros(1000))
        vals[5] = 1
        result = vals.ewm(span=100, adjust=False).mean().sum()
        assert np.abs(result - 1) < 1e-2

    @pytest.mark.parametrize("adjust", [True, False])
    @pytest.mark.parametrize("ignore_na", [True, False])
    def test_ewma_cases(self, adjust, ignore_na):
        # try adjust/ignore_na args matrix

        s = Series([1.0, 2.0, 4.0, 8.0])

        if adjust:
            expected = Series([1.0, 1.6, 2.736842, 4.923077])
        else:
            expected = Series([1.0, 1.333333, 2.222222, 4.148148])

        result = s.ewm(com=2.0, adjust=adjust, ignore_na=ignore_na).mean()
        tm.assert_series_equal(result, expected)

    def test_ewma_nan_handling(self):
        s = Series([1.0] + [np.nan] * 5 + [1.0])
        result = s.ewm(com=5).mean()
        tm.assert_series_equal(result, Series([1.0] * len(s)))

        s = Series([np.nan] * 2 + [1.0] + [np.nan] * 2 + [1.0])
        result = s.ewm(com=5).mean()
        tm.assert_series_equal(result, Series([np.nan] * 2 + [1.0] * 4))

        # GH 7603
        s0 = Series([np.nan, 1.0, 101.0])
        s1 = Series([1.0, np.nan, 101.0])
        s2 = Series([np.nan, 1.0, np.nan, np.nan, 101.0, np.nan])
        s3 = Series([1.0, np.nan, 101.0, 50.0])
        com = 2.0
        alpha = 1.0 / (1.0 + com)

        def simple_wma(s, w):
            return (s.multiply(w).cumsum() / w.cumsum()).fillna(method="ffill")

        for (s, adjust, ignore_na, w) in [
            (s0, True, False, [np.nan, (1.0 - alpha), 1.0]),
            (s0, True, True, [np.nan, (1.0 - alpha), 1.0]),
            (s0, False, False, [np.nan, (1.0 - alpha), alpha]),
            (s0, False, True, [np.nan, (1.0 - alpha), alpha]),
            (s1, True, False, [(1.0 - alpha) ** 2, np.nan, 1.0]),
            (s1, True, True, [(1.0 - alpha), np.nan, 1.0]),
            (s1, False, False, [(1.0 - alpha) ** 2, np.nan, alpha]),
            (s1, False, True, [(1.0 - alpha), np.nan, alpha]),
            (
                s2,
                True,
                False,
                [np.nan, (1.0 - alpha) ** 3, np.nan, np.nan, 1.0, np.nan],
            ),
            (s2, True, True, [np.nan, (1.0 - alpha), np.nan, np.nan, 1.0, np.nan]),
            (
                s2,
                False,
                False,
                [np.nan, (1.0 - alpha) ** 3, np.nan, np.nan, alpha, np.nan],
            ),
            (s2, False, True, [np.nan, (1.0 - alpha), np.nan, np.nan, alpha, np.nan]),
            (s3, True, False, [(1.0 - alpha) ** 3, np.nan, (1.0 - alpha), 1.0]),
            (s3, True, True, [(1.0 - alpha) ** 2, np.nan, (1.0 - alpha), 1.0]),
            (
                s3,
                False,
                False,
                [
                    (1.0 - alpha) ** 3,
                    np.nan,
                    (1.0 - alpha) * alpha,
                    alpha * ((1.0 - alpha) ** 2 + alpha),
                ],
            ),
            (
                s3,
                False,
                True,
                [(1.0 - alpha) ** 2, np.nan, (1.0 - alpha) * alpha, alpha],
            ),
        ]:
            expected = simple_wma(s, Series(w))
            result = s.ewm(com=com, adjust=adjust, ignore_na=ignore_na).mean()

            tm.assert_series_equal(result, expected)
            if ignore_na is False:
                # check that ignore_na defaults to False
                result = s.ewm(com=com, adjust=adjust).mean()
                tm.assert_series_equal(result, expected)

    def test_ewmvar(self):
        self._check_ew(name="var")

    def test_ewmvol(self):
        self._check_ew(name="vol")

    def test_ewma_span_com_args(self):
        A = self.series.ewm(com=9.5).mean()
        B = self.series.ewm(span=20).mean()
        tm.assert_almost_equal(A, B)

        with pytest.raises(ValueError):
            self.series.ewm(com=9.5, span=20)
        with pytest.raises(ValueError):
            self.series.ewm().mean()

    def test_ewma_halflife_arg(self):
        A = self.series.ewm(com=13.932726172912965).mean()
        B = self.series.ewm(halflife=10.0).mean()
        tm.assert_almost_equal(A, B)

        with pytest.raises(ValueError):
            self.series.ewm(span=20, halflife=50)
        with pytest.raises(ValueError):
            self.series.ewm(com=9.5, halflife=50)
        with pytest.raises(ValueError):
            self.series.ewm(com=9.5, span=20, halflife=50)
        with pytest.raises(ValueError):
            self.series.ewm()

    def test_ewm_alpha(self):
        # GH 10789
        s = Series(self.arr)
        a = s.ewm(alpha=0.61722699889169674).mean()
        b = s.ewm(com=0.62014947789973052).mean()
        c = s.ewm(span=2.240298955799461).mean()
        d = s.ewm(halflife=0.721792864318).mean()
        tm.assert_series_equal(a, b)
        tm.assert_series_equal(a, c)
        tm.assert_series_equal(a, d)

    def test_ewm_alpha_arg(self):
        # GH 10789
        s = self.series
        with pytest.raises(ValueError):
            s.ewm()
        with pytest.raises(ValueError):
            s.ewm(com=10.0, alpha=0.5)
        with pytest.raises(ValueError):
            s.ewm(span=10.0, alpha=0.5)
        with pytest.raises(ValueError):
            s.ewm(halflife=10.0, alpha=0.5)

    def test_ewm_domain_checks(self):
        # GH 12492
        s = Series(self.arr)
        msg = "comass must satisfy: comass >= 0"
        with pytest.raises(ValueError, match=msg):
            s.ewm(com=-0.1)
        s.ewm(com=0.0)
        s.ewm(com=0.1)

        msg = "span must satisfy: span >= 1"
        with pytest.raises(ValueError, match=msg):
            s.ewm(span=-0.1)
        with pytest.raises(ValueError, match=msg):
            s.ewm(span=0.0)
        with pytest.raises(ValueError, match=msg):
            s.ewm(span=0.9)
        s.ewm(span=1.0)
        s.ewm(span=1.1)

        msg = "halflife must satisfy: halflife > 0"
        with pytest.raises(ValueError, match=msg):
            s.ewm(halflife=-0.1)
        with pytest.raises(ValueError, match=msg):
            s.ewm(halflife=0.0)
        s.ewm(halflife=0.1)

        msg = "alpha must satisfy: 0 < alpha <= 1"
        with pytest.raises(ValueError, match=msg):
            s.ewm(alpha=-0.1)
        with pytest.raises(ValueError, match=msg):
            s.ewm(alpha=0.0)
        s.ewm(alpha=0.1)
        s.ewm(alpha=1.0)
        with pytest.raises(ValueError, match=msg):
            s.ewm(alpha=1.1)

    @pytest.mark.parametrize("method", ["mean", "vol", "var"])
    def test_ew_empty_series(self, method):
        vals = pd.Series([], dtype=np.float64)

        ewm = vals.ewm(3)
        result = getattr(ewm, method)()
        tm.assert_almost_equal(result, vals)

    def _check_ew(self, name=None, preserve_nan=False):
        series_result = getattr(self.series.ewm(com=10), name)()
        assert isinstance(series_result, Series)

        frame_result = getattr(self.frame.ewm(com=10), name)()
        assert type(frame_result) == DataFrame

        result = getattr(self.series.ewm(com=10), name)()
        if preserve_nan:
            assert result[self._nan_locs].isna().all()

        # excluding NaNs correctly
        arr = randn(50)
        arr[:10] = np.NaN
        arr[-10:] = np.NaN
        s = Series(arr)

        # check min_periods
        # GH 7898
        result = getattr(s.ewm(com=50, min_periods=2), name)()
        assert result[:11].isna().all()
        assert not result[11:].isna().any()

        for min_periods in (0, 1):
            result = getattr(s.ewm(com=50, min_periods=min_periods), name)()
            if name == "mean":
                assert result[:10].isna().all()
                assert not result[10:].isna().any()
            else:
                # ewm.std, ewm.vol, ewm.var (with bias=False) require at least
                # two values
                assert result[:11].isna().all()
                assert not result[11:].isna().any()

            # check series of length 0
            result = getattr(Series().ewm(com=50, min_periods=min_periods), name)()
            tm.assert_series_equal(result, Series())

            # check series of length 1
            result = getattr(Series([1.0]).ewm(50, min_periods=min_periods), name)()
            if name == "mean":
                tm.assert_series_equal(result, Series([1.0]))
            else:
                # ewm.std, ewm.vol, ewm.var with bias=False require at least
                # two values
                tm.assert_series_equal(result, Series([np.NaN]))

        # pass in ints
        result2 = getattr(Series(np.arange(50)).ewm(span=10), name)()
        assert result2.dtype == np.float_


class TestPairwise:

    # GH 7738
    df1s = [
        DataFrame([[2, 4], [1, 2], [5, 2], [8, 1]], columns=[0, 1]),
        DataFrame([[2, 4], [1, 2], [5, 2], [8, 1]], columns=[1, 0]),
        DataFrame([[2, 4], [1, 2], [5, 2], [8, 1]], columns=[1, 1]),
        DataFrame([[2, 4], [1, 2], [5, 2], [8, 1]], columns=["C", "C"]),
        DataFrame([[2, 4], [1, 2], [5, 2], [8, 1]], columns=[1.0, 0]),
        DataFrame([[2, 4], [1, 2], [5, 2], [8, 1]], columns=[0.0, 1]),
        DataFrame([[2, 4], [1, 2], [5, 2], [8, 1]], columns=["C", 1]),
        DataFrame([[2.0, 4.0], [1.0, 2.0], [5.0, 2.0], [8.0, 1.0]], columns=[1, 0.0]),
        DataFrame([[2, 4.0], [1, 2.0], [5, 2.0], [8, 1.0]], columns=[0, 1.0]),
        DataFrame([[2, 4], [1, 2], [5, 2], [8, 1.0]], columns=[1.0, "X"]),
    ]
    df2 = DataFrame(
        [[None, 1, 1], [None, 1, 2], [None, 3, 2], [None, 8, 1]],
        columns=["Y", "Z", "X"],
    )
    s = Series([1, 1, 3, 8])

    def compare(self, result, expected):

        # since we have sorted the results
        # we can only compare non-nans
        result = result.dropna().values
        expected = expected.dropna().values

        tm.assert_numpy_array_equal(result, expected, check_dtype=False)

    @pytest.mark.parametrize("f", [lambda x: x.cov(), lambda x: x.corr()])
    def test_no_flex(self, f):

        # DataFrame methods (which do not call _flex_binary_moment())

        results = [f(df) for df in self.df1s]
        for (df, result) in zip(self.df1s, results):
            tm.assert_index_equal(result.index, df.columns)
            tm.assert_index_equal(result.columns, df.columns)
        for i, result in enumerate(results):
            if i > 0:
                self.compare(result, results[0])

    @pytest.mark.parametrize(
        "f",
        [
            lambda x: x.expanding().cov(pairwise=True),
            lambda x: x.expanding().corr(pairwise=True),
            lambda x: x.rolling(window=3).cov(pairwise=True),
            lambda x: x.rolling(window=3).corr(pairwise=True),
            lambda x: x.ewm(com=3).cov(pairwise=True),
            lambda x: x.ewm(com=3).corr(pairwise=True),
        ],
    )
    def test_pairwise_with_self(self, f):

        # DataFrame with itself, pairwise=True
        # note that we may construct the 1st level of the MI
        # in a non-monotonic way, so compare accordingly
        results = []
        for i, df in enumerate(self.df1s):
            result = f(df)
            tm.assert_index_equal(result.index.levels[0], df.index, check_names=False)
            tm.assert_numpy_array_equal(
                safe_sort(result.index.levels[1]), safe_sort(df.columns.unique())
            )
            tm.assert_index_equal(result.columns, df.columns)
            results.append(df)

        for i, result in enumerate(results):
            if i > 0:
                self.compare(result, results[0])

    @pytest.mark.parametrize(
        "f",
        [
            lambda x: x.expanding().cov(pairwise=False),
            lambda x: x.expanding().corr(pairwise=False),
            lambda x: x.rolling(window=3).cov(pairwise=False),
            lambda x: x.rolling(window=3).corr(pairwise=False),
            lambda x: x.ewm(com=3).cov(pairwise=False),
            lambda x: x.ewm(com=3).corr(pairwise=False),
        ],
    )
    def test_no_pairwise_with_self(self, f):

        # DataFrame with itself, pairwise=False
        results = [f(df) for df in self.df1s]
        for (df, result) in zip(self.df1s, results):
            tm.assert_index_equal(result.index, df.index)
            tm.assert_index_equal(result.columns, df.columns)
        for i, result in enumerate(results):
            if i > 0:
                self.compare(result, results[0])

    @pytest.mark.parametrize(
        "f",
        [
            lambda x, y: x.expanding().cov(y, pairwise=True),
            lambda x, y: x.expanding().corr(y, pairwise=True),
            lambda x, y: x.rolling(window=3).cov(y, pairwise=True),
            lambda x, y: x.rolling(window=3).corr(y, pairwise=True),
            lambda x, y: x.ewm(com=3).cov(y, pairwise=True),
            lambda x, y: x.ewm(com=3).corr(y, pairwise=True),
        ],
    )
    def test_pairwise_with_other(self, f):

        # DataFrame with another DataFrame, pairwise=True
        results = [f(df, self.df2) for df in self.df1s]
        for (df, result) in zip(self.df1s, results):
            tm.assert_index_equal(result.index.levels[0], df.index, check_names=False)
            tm.assert_numpy_array_equal(
                safe_sort(result.index.levels[1]), safe_sort(self.df2.columns.unique())
            )
        for i, result in enumerate(results):
            if i > 0:
                self.compare(result, results[0])

    @pytest.mark.parametrize(
        "f",
        [
            lambda x, y: x.expanding().cov(y, pairwise=False),
            lambda x, y: x.expanding().corr(y, pairwise=False),
            lambda x, y: x.rolling(window=3).cov(y, pairwise=False),
            lambda x, y: x.rolling(window=3).corr(y, pairwise=False),
            lambda x, y: x.ewm(com=3).cov(y, pairwise=False),
            lambda x, y: x.ewm(com=3).corr(y, pairwise=False),
        ],
    )
    def test_no_pairwise_with_other(self, f):

        # DataFrame with another DataFrame, pairwise=False
        results = [
            f(df, self.df2) if df.columns.is_unique else None for df in self.df1s
        ]
        for (df, result) in zip(self.df1s, results):
            if result is not None:
                with catch_warnings(record=True):
                    warnings.simplefilter("ignore", RuntimeWarning)
                    # we can have int and str columns
                    expected_index = df.index.union(self.df2.index)
                    expected_columns = df.columns.union(self.df2.columns)
                tm.assert_index_equal(result.index, expected_index)
                tm.assert_index_equal(result.columns, expected_columns)
            else:
                with pytest.raises(ValueError, match="'arg1' columns are not unique"):
                    f(df, self.df2)
                with pytest.raises(ValueError, match="'arg2' columns are not unique"):
                    f(self.df2, df)

    @pytest.mark.parametrize(
        "f",
        [
            lambda x, y: x.expanding().cov(y),
            lambda x, y: x.expanding().corr(y),
            lambda x, y: x.rolling(window=3).cov(y),
            lambda x, y: x.rolling(window=3).corr(y),
            lambda x, y: x.ewm(com=3).cov(y),
            lambda x, y: x.ewm(com=3).corr(y),
        ],
    )
    def test_pairwise_with_series(self, f):

        # DataFrame with a Series
        results = [f(df, self.s) for df in self.df1s] + [
            f(self.s, df) for df in self.df1s
        ]
        for (df, result) in zip(self.df1s, results):
            tm.assert_index_equal(result.index, df.index)
            tm.assert_index_equal(result.columns, df.columns)
        for i, result in enumerate(results):
            if i > 0:
                self.compare(result, results[0])


# create the data only once as we are not setting it
def _create_consistency_data():
    def create_series():
        return [
            Series(),
            Series([np.nan]),
            Series([np.nan, np.nan]),
            Series([3.0]),
            Series([np.nan, 3.0]),
            Series([3.0, np.nan]),
            Series([1.0, 3.0]),
            Series([2.0, 2.0]),
            Series([3.0, 1.0]),
            Series(
                [5.0, 5.0, 5.0, 5.0, np.nan, np.nan, np.nan, 5.0, 5.0, np.nan, np.nan]
            ),
            Series(
                [
                    np.nan,
                    5.0,
                    5.0,
                    5.0,
                    np.nan,
                    np.nan,
                    np.nan,
                    5.0,
                    5.0,
                    np.nan,
                    np.nan,
                ]
            ),
            Series(
                [
                    np.nan,
                    np.nan,
                    5.0,
                    5.0,
                    np.nan,
                    np.nan,
                    np.nan,
                    5.0,
                    5.0,
                    np.nan,
                    np.nan,
                ]
            ),
            Series(
                [
                    np.nan,
                    3.0,
                    np.nan,
                    3.0,
                    4.0,
                    5.0,
                    6.0,
                    np.nan,
                    np.nan,
                    7.0,
                    12.0,
                    13.0,
                    14.0,
                    15.0,
                ]
            ),
            Series(
                [
                    np.nan,
                    5.0,
                    np.nan,
                    2.0,
                    4.0,
                    0.0,
                    9.0,
                    np.nan,
                    np.nan,
                    3.0,
                    12.0,
                    13.0,
                    14.0,
                    15.0,
                ]
            ),
            Series(
                [
                    2.0,
                    3.0,
                    np.nan,
                    3.0,
                    4.0,
                    5.0,
                    6.0,
                    np.nan,
                    np.nan,
                    7.0,
                    12.0,
                    13.0,
                    14.0,
                    15.0,
                ]
            ),
            Series(
                [
                    2.0,
                    5.0,
                    np.nan,
                    2.0,
                    4.0,
                    0.0,
                    9.0,
                    np.nan,
                    np.nan,
                    3.0,
                    12.0,
                    13.0,
                    14.0,
                    15.0,
                ]
            ),
            Series(range(10)),
            Series(range(20, 0, -2)),
        ]

    def create_dataframes():
        return [
            DataFrame(),
            DataFrame(columns=["a"]),
            DataFrame(columns=["a", "a"]),
            DataFrame(columns=["a", "b"]),
            DataFrame(np.arange(10).reshape((5, 2))),
            DataFrame(np.arange(25).reshape((5, 5))),
            DataFrame(np.arange(25).reshape((5, 5)), columns=["a", "b", 99, "d", "d"]),
        ] + [DataFrame(s) for s in create_series()]

    def is_constant(x):
        values = x.values.ravel()
        return len(set(values[notna(values)])) == 1

    def no_nans(x):
        return x.notna().all().all()

    # data is a tuple(object, is_constant, no_nans)
    data = create_series() + create_dataframes()

    return [(x, is_constant(x), no_nans(x)) for x in data]


_consistency_data = _create_consistency_data()


def _rolling_consistency_cases():
    for window in [1, 2, 3, 10, 20]:
        for min_periods in {0, 1, 2, 3, 4, window}:
            if min_periods and (min_periods > window):
                continue
            for center in [False, True]:
                yield window, min_periods, center


class TestMomentsConsistency(Base):
    base_functions = [
        (lambda v: Series(v).count(), None, "count"),
        (lambda v: Series(v).max(), None, "max"),
        (lambda v: Series(v).min(), None, "min"),
        (lambda v: Series(v).sum(), None, "sum"),
        (lambda v: Series(v).mean(), None, "mean"),
        (lambda v: Series(v).std(), 1, "std"),
        (lambda v: Series(v).cov(Series(v)), None, "cov"),
        (lambda v: Series(v).corr(Series(v)), None, "corr"),
        (lambda v: Series(v).var(), 1, "var"),
        # restore once GH 8086 is fixed
        # lambda v: Series(v).skew(), 3, 'skew'),
        # (lambda v: Series(v).kurt(), 4, 'kurt'),
        # restore once GH 8084 is fixed
        # lambda v: Series(v).quantile(0.3), None, 'quantile'),
        (lambda v: Series(v).median(), None, "median"),
        (np.nanmax, 1, "max"),
        (np.nanmin, 1, "min"),
        (np.nansum, 1, "sum"),
        (np.nanmean, 1, "mean"),
        (lambda v: np.nanstd(v, ddof=1), 1, "std"),
        (lambda v: np.nanvar(v, ddof=1), 1, "var"),
        (np.nanmedian, 1, "median"),
    ]
    no_nan_functions = [
        (np.max, None, "max"),
        (np.min, None, "min"),
        (np.sum, None, "sum"),
        (np.mean, None, "mean"),
        (lambda v: np.std(v, ddof=1), 1, "std"),
        (lambda v: np.var(v, ddof=1), 1, "var"),
        (np.median, None, "median"),
    ]

    def _create_data(self):
        super()._create_data()
        self.data = _consistency_data

    def setup_method(self, method):
        self._create_data()

    def _test_moments_consistency(
        self,
        min_periods,
        count,
        mean,
        mock_mean,
        corr,
        var_unbiased=None,
        std_unbiased=None,
        cov_unbiased=None,
        var_biased=None,
        std_biased=None,
        cov_biased=None,
        var_debiasing_factors=None,
    ):
        def _non_null_values(x):
            values = x.values.ravel()
            return set(values[notna(values)].tolist())

        for (x, is_constant, no_nans) in self.data:
            count_x = count(x)
            mean_x = mean(x)

            if mock_mean:
                # check that mean equals mock_mean
                expected = mock_mean(x)
                assert_equal(mean_x, expected.astype("float64"))

            # check that correlation of a series with itself is either 1 or NaN
            corr_x_x = corr(x, x)

            # assert _non_null_values(corr_x_x).issubset(set([1.]))
            # restore once rolling_cov(x, x) is identically equal to var(x)

            if is_constant:
                exp = x.max() if isinstance(x, Series) else x.max().max()

                # check mean of constant series
                expected = x * np.nan
                expected[count_x >= max(min_periods, 1)] = exp
                assert_equal(mean_x, expected)

                # check correlation of constant series with itself is NaN
                expected[:] = np.nan
                assert_equal(corr_x_x, expected)

            if var_unbiased and var_biased and var_debiasing_factors:
                # check variance debiasing factors
                var_unbiased_x = var_unbiased(x)
                var_biased_x = var_biased(x)
                var_debiasing_factors_x = var_debiasing_factors(x)
                assert_equal(var_unbiased_x, var_biased_x * var_debiasing_factors_x)

            for (std, var, cov) in [
                (std_biased, var_biased, cov_biased),
                (std_unbiased, var_unbiased, cov_unbiased),
            ]:

                # check that var(x), std(x), and cov(x) are all >= 0
                var_x = var(x)
                std_x = std(x)
                assert not (var_x < 0).any().any()
                assert not (std_x < 0).any().any()
                if cov:
                    cov_x_x = cov(x, x)
                    assert not (cov_x_x < 0).any().any()

                    # check that var(x) == cov(x, x)
                    assert_equal(var_x, cov_x_x)

                # check that var(x) == std(x)^2
                assert_equal(var_x, std_x * std_x)

                if var is var_biased:
                    # check that biased var(x) == mean(x^2) - mean(x)^2
                    mean_x2 = mean(x * x)
                    assert_equal(var_x, mean_x2 - (mean_x * mean_x))

                if is_constant:
                    # check that variance of constant series is identically 0
                    assert not (var_x > 0).any().any()
                    expected = x * np.nan
                    expected[count_x >= max(min_periods, 1)] = 0.0
                    if var is var_unbiased:
                        expected[count_x < 2] = np.nan
                    assert_equal(var_x, expected)

                if isinstance(x, Series):
                    for (y, is_constant, no_nans) in self.data:
                        if not x.isna().equals(y.isna()):
                            # can only easily test two Series with similar
                            # structure
                            continue

                        # check that cor(x, y) is symmetric
                        corr_x_y = corr(x, y)
                        corr_y_x = corr(y, x)
                        assert_equal(corr_x_y, corr_y_x)

                        if cov:
                            # check that cov(x, y) is symmetric
                            cov_x_y = cov(x, y)
                            cov_y_x = cov(y, x)
                            assert_equal(cov_x_y, cov_y_x)

                            # check that cov(x, y) == (var(x+y) - var(x) -
                            # var(y)) / 2
                            var_x_plus_y = var(x + y)
                            var_y = var(y)
                            assert_equal(cov_x_y, 0.5 * (var_x_plus_y - var_x - var_y))

                            # check that corr(x, y) == cov(x, y) / (std(x) *
                            # std(y))
                            std_y = std(y)
                            assert_equal(corr_x_y, cov_x_y / (std_x * std_y))

                            if cov is cov_biased:
                                # check that biased cov(x, y) == mean(x*y) -
                                # mean(x)*mean(y)
                                mean_y = mean(y)
                                mean_x_times_y = mean(x * y)
                                assert_equal(
                                    cov_x_y, mean_x_times_y - (mean_x * mean_y)
                                )

    @pytest.mark.slow
    @pytest.mark.parametrize("min_periods", [0, 1, 2, 3, 4])
    @pytest.mark.parametrize("adjust", [True, False])
    @pytest.mark.parametrize("ignore_na", [True, False])
    def test_ewm_consistency(self, min_periods, adjust, ignore_na):
        def _weights(s, com, adjust, ignore_na):
            if isinstance(s, DataFrame):
                if not len(s.columns):
                    return DataFrame(index=s.index, columns=s.columns)
                w = concat(
                    [
                        _weights(
                            s.iloc[:, i], com=com, adjust=adjust, ignore_na=ignore_na
                        )
                        for i, _ in enumerate(s.columns)
                    ],
                    axis=1,
                )
                w.index = s.index
                w.columns = s.columns
                return w

            w = Series(np.nan, index=s.index)
            alpha = 1.0 / (1.0 + com)
            if ignore_na:
                w[s.notna()] = _weights(
                    s[s.notna()], com=com, adjust=adjust, ignore_na=False
                )
            elif adjust:
                for i in range(len(s)):
                    if s.iat[i] == s.iat[i]:
                        w.iat[i] = pow(1.0 / (1.0 - alpha), i)
            else:
                sum_wts = 0.0
                prev_i = -1
                for i in range(len(s)):
                    if s.iat[i] == s.iat[i]:
                        if prev_i == -1:
                            w.iat[i] = 1.0
                        else:
                            w.iat[i] = alpha * sum_wts / pow(1.0 - alpha, i - prev_i)
                        sum_wts += w.iat[i]
                        prev_i = i
            return w

        def _variance_debiasing_factors(s, com, adjust, ignore_na):
            weights = _weights(s, com=com, adjust=adjust, ignore_na=ignore_na)
            cum_sum = weights.cumsum().fillna(method="ffill")
            cum_sum_sq = (weights * weights).cumsum().fillna(method="ffill")
            numerator = cum_sum * cum_sum
            denominator = numerator - cum_sum_sq
            denominator[denominator <= 0.0] = np.nan
            return numerator / denominator

        def _ewma(s, com, min_periods, adjust, ignore_na):
            weights = _weights(s, com=com, adjust=adjust, ignore_na=ignore_na)
            result = (
                s.multiply(weights)
                .cumsum()
                .divide(weights.cumsum())
                .fillna(method="ffill")
            )
            result[
                s.expanding().count() < (max(min_periods, 1) if min_periods else 1)
            ] = np.nan
            return result

        com = 3.0
        # test consistency between different ewm* moments
        self._test_moments_consistency(
            min_periods=min_periods,
            count=lambda x: x.expanding().count(),
            mean=lambda x: x.ewm(
                com=com, min_periods=min_periods, adjust=adjust, ignore_na=ignore_na
            ).mean(),
            mock_mean=lambda x: _ewma(
                x, com=com, min_periods=min_periods, adjust=adjust, ignore_na=ignore_na
            ),
            corr=lambda x, y: x.ewm(
                com=com, min_periods=min_periods, adjust=adjust, ignore_na=ignore_na
            ).corr(y),
            var_unbiased=lambda x: (
                x.ewm(
                    com=com, min_periods=min_periods, adjust=adjust, ignore_na=ignore_na
                ).var(bias=False)
            ),
            std_unbiased=lambda x: (
                x.ewm(
                    com=com, min_periods=min_periods, adjust=adjust, ignore_na=ignore_na
                ).std(bias=False)
            ),
            cov_unbiased=lambda x, y: (
                x.ewm(
                    com=com, min_periods=min_periods, adjust=adjust, ignore_na=ignore_na
                ).cov(y, bias=False)
            ),
            var_biased=lambda x: (
                x.ewm(
                    com=com, min_periods=min_periods, adjust=adjust, ignore_na=ignore_na
                ).var(bias=True)
            ),
            std_biased=lambda x: x.ewm(
                com=com, min_periods=min_periods, adjust=adjust, ignore_na=ignore_na
            ).std(bias=True),
            cov_biased=lambda x, y: (
                x.ewm(
                    com=com, min_periods=min_periods, adjust=adjust, ignore_na=ignore_na
                ).cov(y, bias=True)
            ),
            var_debiasing_factors=lambda x: (
                _variance_debiasing_factors(
                    x, com=com, adjust=adjust, ignore_na=ignore_na
                )
            ),
        )

    @pytest.mark.slow
    @pytest.mark.parametrize("min_periods", [0, 1, 2, 3, 4])
    def test_expanding_consistency(self, min_periods):

        # suppress warnings about empty slices, as we are deliberately testing
        # with empty/0-length Series/DataFrames
        with warnings.catch_warnings():
            warnings.filterwarnings(
                "ignore",
                message=".*(empty slice|0 for slice).*",
                category=RuntimeWarning,
            )

            # test consistency between different expanding_* moments
            self._test_moments_consistency(
                min_periods=min_periods,
                count=lambda x: x.expanding().count(),
                mean=lambda x: x.expanding(min_periods=min_periods).mean(),
                mock_mean=lambda x: x.expanding(min_periods=min_periods).sum()
                / x.expanding().count(),
                corr=lambda x, y: x.expanding(min_periods=min_periods).corr(y),
                var_unbiased=lambda x: x.expanding(min_periods=min_periods).var(),
                std_unbiased=lambda x: x.expanding(min_periods=min_periods).std(),
                cov_unbiased=lambda x, y: x.expanding(min_periods=min_periods).cov(y),
                var_biased=lambda x: x.expanding(min_periods=min_periods).var(ddof=0),
                std_biased=lambda x: x.expanding(min_periods=min_periods).std(ddof=0),
                cov_biased=lambda x, y: x.expanding(min_periods=min_periods).cov(
                    y, ddof=0
                ),
                var_debiasing_factors=lambda x: (
                    x.expanding().count()
                    / (x.expanding().count() - 1.0).replace(0.0, np.nan)
                ),
            )

            # test consistency between expanding_xyz() and either (a)
            # expanding_apply of Series.xyz(), or (b) expanding_apply of
            # np.nanxyz()
            for (x, is_constant, no_nans) in self.data:
                functions = self.base_functions

                # GH 8269
                if no_nans:
                    functions = self.base_functions + self.no_nan_functions
                for (f, require_min_periods, name) in functions:
                    expanding_f = getattr(x.expanding(min_periods=min_periods), name)

                    if (
                        require_min_periods
                        and (min_periods is not None)
                        and (min_periods < require_min_periods)
                    ):
                        continue

                    if name == "count":
                        expanding_f_result = expanding_f()
                        expanding_apply_f_result = x.expanding(min_periods=0).apply(
                            func=f, raw=True
                        )
                    else:
                        if name in ["cov", "corr"]:
                            expanding_f_result = expanding_f(pairwise=False)
                        else:
                            expanding_f_result = expanding_f()
                        expanding_apply_f_result = x.expanding(
                            min_periods=min_periods
                        ).apply(func=f, raw=True)

                    # GH 9422
                    if name in ["sum", "prod"]:
                        assert_equal(expanding_f_result, expanding_apply_f_result)

    @pytest.mark.slow
    @pytest.mark.parametrize(
        "window,min_periods,center", list(_rolling_consistency_cases())
    )
    def test_rolling_consistency(self, window, min_periods, center):

        # suppress warnings about empty slices, as we are deliberately testing
        # with empty/0-length Series/DataFrames
        with warnings.catch_warnings():
            warnings.filterwarnings(
                "ignore",
                message=".*(empty slice|0 for slice).*",
                category=RuntimeWarning,
            )

            # test consistency between different rolling_* moments
            self._test_moments_consistency(
                min_periods=min_periods,
                count=lambda x: (x.rolling(window=window, center=center).count()),
                mean=lambda x: (
                    x.rolling(
                        window=window, min_periods=min_periods, center=center
                    ).mean()
                ),
                mock_mean=lambda x: (
                    x.rolling(window=window, min_periods=min_periods, center=center)
                    .sum()
                    .divide(
                        x.rolling(
                            window=window, min_periods=min_periods, center=center
                        ).count()
                    )
                ),
                corr=lambda x, y: (
                    x.rolling(
                        window=window, min_periods=min_periods, center=center
                    ).corr(y)
                ),
                var_unbiased=lambda x: (
                    x.rolling(
                        window=window, min_periods=min_periods, center=center
                    ).var()
                ),
                std_unbiased=lambda x: (
                    x.rolling(
                        window=window, min_periods=min_periods, center=center
                    ).std()
                ),
                cov_unbiased=lambda x, y: (
                    x.rolling(
                        window=window, min_periods=min_periods, center=center
                    ).cov(y)
                ),
                var_biased=lambda x: (
                    x.rolling(
                        window=window, min_periods=min_periods, center=center
                    ).var(ddof=0)
                ),
                std_biased=lambda x: (
                    x.rolling(
                        window=window, min_periods=min_periods, center=center
                    ).std(ddof=0)
                ),
                cov_biased=lambda x, y: (
                    x.rolling(
                        window=window, min_periods=min_periods, center=center
                    ).cov(y, ddof=0)
                ),
                var_debiasing_factors=lambda x: (
                    x.rolling(window=window, center=center)
                    .count()
                    .divide(
                        (x.rolling(window=window, center=center).count() - 1.0).replace(
                            0.0, np.nan
                        )
                    )
                ),
            )

            # test consistency between rolling_xyz() and either (a)
            # rolling_apply of Series.xyz(), or (b) rolling_apply of
            # np.nanxyz()
            for (x, is_constant, no_nans) in self.data:
                functions = self.base_functions

                # GH 8269
                if no_nans:
                    functions = self.base_functions + self.no_nan_functions
                for (f, require_min_periods, name) in functions:
                    rolling_f = getattr(
                        x.rolling(
                            window=window, center=center, min_periods=min_periods
                        ),
                        name,
                    )

                    if (
                        require_min_periods
                        and (min_periods is not None)
                        and (min_periods < require_min_periods)
                    ):
                        continue

                    if name == "count":
                        rolling_f_result = rolling_f()
                        rolling_apply_f_result = x.rolling(
                            window=window, min_periods=0, center=center
                        ).apply(func=f, raw=True)
                    else:
                        if name in ["cov", "corr"]:
                            rolling_f_result = rolling_f(pairwise=False)
                        else:
                            rolling_f_result = rolling_f()
                        rolling_apply_f_result = x.rolling(
                            window=window, min_periods=min_periods, center=center
                        ).apply(func=f, raw=True)

                    # GH 9422
                    if name in ["sum", "prod"]:
                        assert_equal(rolling_f_result, rolling_apply_f_result)

    # binary moments
    def test_rolling_cov(self):
        A = self.series
        B = A + randn(len(A))

        result = A.rolling(window=50, min_periods=25).cov(B)
        tm.assert_almost_equal(result[-1], np.cov(A[-50:], B[-50:])[0, 1])

    def test_rolling_cov_pairwise(self):
        self._check_pairwise_moment("rolling", "cov", window=10, min_periods=5)

    def test_rolling_corr(self):
        A = self.series
        B = A + randn(len(A))

        result = A.rolling(window=50, min_periods=25).corr(B)
        tm.assert_almost_equal(result[-1], np.corrcoef(A[-50:], B[-50:])[0, 1])

        # test for correct bias correction
        a = tm.makeTimeSeries()
        b = tm.makeTimeSeries()
        a[:5] = np.nan
        b[:10] = np.nan

        result = a.rolling(window=len(a), min_periods=1).corr(b)
        tm.assert_almost_equal(result[-1], a.corr(b))

    def test_rolling_corr_pairwise(self):
        self._check_pairwise_moment("rolling", "corr", window=10, min_periods=5)

    @pytest.mark.parametrize("window", range(7))
    def test_rolling_corr_with_zero_variance(self, window):
        # GH 18430
        s = pd.Series(np.zeros(20))
        other = pd.Series(np.arange(20))

        assert s.rolling(window=window).corr(other=other).isna().all()

    def _check_pairwise_moment(self, dispatch, name, **kwargs):
        def get_result(obj, obj2=None):
            return getattr(getattr(obj, dispatch)(**kwargs), name)(obj2)

        result = get_result(self.frame)
        result = result.loc[(slice(None), 1), 5]
        result.index = result.index.droplevel(1)
        expected = get_result(self.frame[1], self.frame[5])
        tm.assert_series_equal(result, expected, check_names=False)

    def test_flex_binary_moment(self):
        # GH3155
        # don't blow the stack
        msg = (
            "arguments to moment function must be of type"
            " np.ndarray/Series/DataFrame"
        )
        with pytest.raises(TypeError, match=msg):
            rwindow._flex_binary_moment(5, 6, None)

    def test_corr_sanity(self):
        # GH 3155
        df = DataFrame(
            np.array(
                [
                    [0.87024726, 0.18505595],
                    [0.64355431, 0.3091617],
                    [0.92372966, 0.50552513],
                    [0.00203756, 0.04520709],
                    [0.84780328, 0.33394331],
                    [0.78369152, 0.63919667],
                ]
            )
        )

        res = df[0].rolling(5, center=True).corr(df[1])
        assert all(np.abs(np.nan_to_num(x)) <= 1 for x in res)

        # and some fuzzing
        for _ in range(10):
            df = DataFrame(np.random.rand(30, 2))
            res = df[0].rolling(5, center=True).corr(df[1])
            try:
                assert all(np.abs(np.nan_to_num(x)) <= 1 for x in res)
            except AssertionError:
                print(res)

    @pytest.mark.parametrize("method", ["corr", "cov"])
    def test_flex_binary_frame(self, method):
        series = self.frame[1]

        res = getattr(series.rolling(window=10), method)(self.frame)
        res2 = getattr(self.frame.rolling(window=10), method)(series)
        exp = self.frame.apply(lambda x: getattr(series.rolling(window=10), method)(x))

        tm.assert_frame_equal(res, exp)
        tm.assert_frame_equal(res2, exp)

        frame2 = self.frame.copy()
        frame2.values[:] = np.random.randn(*frame2.shape)

        res3 = getattr(self.frame.rolling(window=10), method)(frame2)
        exp = DataFrame(
            {
                k: getattr(self.frame[k].rolling(window=10), method)(frame2[k])
                for k in self.frame
            }
        )
        tm.assert_frame_equal(res3, exp)

    def test_ewmcov(self):
        self._check_binary_ew("cov")

    def test_ewmcov_pairwise(self):
        self._check_pairwise_moment("ewm", "cov", span=10, min_periods=5)

    def test_ewmcorr(self):
        self._check_binary_ew("corr")

    def test_ewmcorr_pairwise(self):
        self._check_pairwise_moment("ewm", "corr", span=10, min_periods=5)

    def _check_binary_ew(self, name):
        def func(A, B, com, **kwargs):
            return getattr(A.ewm(com, **kwargs), name)(B)

        A = Series(randn(50), index=np.arange(50))
        B = A[2:] + randn(48)

        A[:10] = np.NaN
        B[-10:] = np.NaN

        result = func(A, B, 20, min_periods=5)
        assert np.isnan(result.values[:14]).all()
        assert not np.isnan(result.values[14:]).any()

        # GH 7898
        for min_periods in (0, 1, 2):
            result = func(A, B, 20, min_periods=min_periods)
            # binary functions (ewmcov, ewmcorr) with bias=False require at
            # least two values
            assert np.isnan(result.values[:11]).all()
            assert not np.isnan(result.values[11:]).any()

            # check series of length 0
            result = func(Series([]), Series([]), 50, min_periods=min_periods)
            tm.assert_series_equal(result, Series([]))

            # check series of length 1
            result = func(Series([1.0]), Series([1.0]), 50, min_periods=min_periods)
            tm.assert_series_equal(result, Series([np.NaN]))

        msg = "Input arrays must be of the same type!"
        # exception raised is Exception
        with pytest.raises(Exception, match=msg):
            func(A, randn(50), 20, min_periods=5)

    def test_expanding_apply_args_kwargs(self, raw):
        def mean_w_arg(x, const):
            return np.mean(x) + const

        df = DataFrame(np.random.rand(20, 3))

        expected = df.expanding().apply(np.mean, raw=raw) + 20.0

        result = df.expanding().apply(mean_w_arg, raw=raw, args=(20,))
        tm.assert_frame_equal(result, expected)

        result = df.expanding().apply(mean_w_arg, raw=raw, kwargs={"const": 20})
        tm.assert_frame_equal(result, expected)

    def test_expanding_corr(self):
        A = self.series.dropna()
        B = (A + randn(len(A)))[:-5]

        result = A.expanding().corr(B)

        rolling_result = A.rolling(window=len(A), min_periods=1).corr(B)

        tm.assert_almost_equal(rolling_result, result)

    def test_expanding_count(self):
        result = self.series.expanding().count()
        tm.assert_almost_equal(
            result, self.series.rolling(window=len(self.series)).count()
        )

    def test_expanding_quantile(self):
        result = self.series.expanding().quantile(0.5)

        rolling_result = self.series.rolling(
            window=len(self.series), min_periods=1
        ).quantile(0.5)

        tm.assert_almost_equal(result, rolling_result)

    def test_expanding_cov(self):
        A = self.series
        B = (A + randn(len(A)))[:-5]

        result = A.expanding().cov(B)

        rolling_result = A.rolling(window=len(A), min_periods=1).cov(B)

        tm.assert_almost_equal(rolling_result, result)

    def test_expanding_cov_pairwise(self):
        result = self.frame.expanding().corr()

        rolling_result = self.frame.rolling(
            window=len(self.frame), min_periods=1
        ).corr()

        tm.assert_frame_equal(result, rolling_result)

    def test_expanding_corr_pairwise(self):
        result = self.frame.expanding().corr()

        rolling_result = self.frame.rolling(
            window=len(self.frame), min_periods=1
        ).corr()
        tm.assert_frame_equal(result, rolling_result)

    def test_expanding_cov_diff_index(self):
        # GH 7512
        s1 = Series([1, 2, 3], index=[0, 1, 2])
        s2 = Series([1, 3], index=[0, 2])
        result = s1.expanding().cov(s2)
        expected = Series([None, None, 2.0])
        tm.assert_series_equal(result, expected)

        s2a = Series([1, None, 3], index=[0, 1, 2])
        result = s1.expanding().cov(s2a)
        tm.assert_series_equal(result, expected)

        s1 = Series([7, 8, 10], index=[0, 1, 3])
        s2 = Series([7, 9, 10], index=[0, 2, 3])
        result = s1.expanding().cov(s2)
        expected = Series([None, None, None, 4.5])
        tm.assert_series_equal(result, expected)

    def test_expanding_corr_diff_index(self):
        # GH 7512
        s1 = Series([1, 2, 3], index=[0, 1, 2])
        s2 = Series([1, 3], index=[0, 2])
        result = s1.expanding().corr(s2)
        expected = Series([None, None, 1.0])
        tm.assert_series_equal(result, expected)

        s2a = Series([1, None, 3], index=[0, 1, 2])
        result = s1.expanding().corr(s2a)
        tm.assert_series_equal(result, expected)

        s1 = Series([7, 8, 10], index=[0, 1, 3])
        s2 = Series([7, 9, 10], index=[0, 2, 3])
        result = s1.expanding().corr(s2)
        expected = Series([None, None, None, 1.0])
        tm.assert_series_equal(result, expected)

    def test_rolling_cov_diff_length(self):
        # GH 7512
        s1 = Series([1, 2, 3], index=[0, 1, 2])
        s2 = Series([1, 3], index=[0, 2])
        result = s1.rolling(window=3, min_periods=2).cov(s2)
        expected = Series([None, None, 2.0])
        tm.assert_series_equal(result, expected)

        s2a = Series([1, None, 3], index=[0, 1, 2])
        result = s1.rolling(window=3, min_periods=2).cov(s2a)
        tm.assert_series_equal(result, expected)

    def test_rolling_corr_diff_length(self):
        # GH 7512
        s1 = Series([1, 2, 3], index=[0, 1, 2])
        s2 = Series([1, 3], index=[0, 2])
        result = s1.rolling(window=3, min_periods=2).corr(s2)
        expected = Series([None, None, 1.0])
        tm.assert_series_equal(result, expected)

        s2a = Series([1, None, 3], index=[0, 1, 2])
        result = s1.rolling(window=3, min_periods=2).corr(s2a)
        tm.assert_series_equal(result, expected)

    @pytest.mark.parametrize(
        "f",
        [
            lambda x: (x.rolling(window=10, min_periods=5).cov(x, pairwise=False)),
            lambda x: (x.rolling(window=10, min_periods=5).corr(x, pairwise=False)),
            lambda x: x.rolling(window=10, min_periods=5).max(),
            lambda x: x.rolling(window=10, min_periods=5).min(),
            lambda x: x.rolling(window=10, min_periods=5).sum(),
            lambda x: x.rolling(window=10, min_periods=5).mean(),
            lambda x: x.rolling(window=10, min_periods=5).std(),
            lambda x: x.rolling(window=10, min_periods=5).var(),
            lambda x: x.rolling(window=10, min_periods=5).skew(),
            lambda x: x.rolling(window=10, min_periods=5).kurt(),
            lambda x: x.rolling(window=10, min_periods=5).quantile(quantile=0.5),
            lambda x: x.rolling(window=10, min_periods=5).median(),
            lambda x: x.rolling(window=10, min_periods=5).apply(sum, raw=False),
            lambda x: x.rolling(window=10, min_periods=5).apply(sum, raw=True),
            lambda x: x.rolling(win_type="boxcar", window=10, min_periods=5).mean(),
        ],
    )
    def test_rolling_functions_window_non_shrinkage(self, f):
        # GH 7764
        s = Series(range(4))
        s_expected = Series(np.nan, index=s.index)
        df = DataFrame([[1, 5], [3, 2], [3, 9], [-1, 0]], columns=["A", "B"])
        df_expected = DataFrame(np.nan, index=df.index, columns=df.columns)

        try:
            s_result = f(s)
            tm.assert_series_equal(s_result, s_expected)

            df_result = f(df)
            tm.assert_frame_equal(df_result, df_expected)
        except (ImportError):

            # scipy needed for rolling_window
            pytest.skip("scipy not available")

    def test_rolling_functions_window_non_shrinkage_binary(self):

        # corr/cov return a MI DataFrame
        df = DataFrame(
            [[1, 5], [3, 2], [3, 9], [-1, 0]],
            columns=Index(["A", "B"], name="foo"),
            index=Index(range(4), name="bar"),
        )
        df_expected = DataFrame(
            columns=Index(["A", "B"], name="foo"),
            index=pd.MultiIndex.from_product(
                [df.index, df.columns], names=["bar", "foo"]
            ),
            dtype="float64",
        )
        functions = [
            lambda x: (x.rolling(window=10, min_periods=5).cov(x, pairwise=True)),
            lambda x: (x.rolling(window=10, min_periods=5).corr(x, pairwise=True)),
        ]
        for f in functions:
            df_result = f(df)
            tm.assert_frame_equal(df_result, df_expected)

    def test_moment_functions_zero_length(self):
        # GH 8056
        s = Series()
        s_expected = s
        df1 = DataFrame()
        df1_expected = df1
        df2 = DataFrame(columns=["a"])
        df2["a"] = df2["a"].astype("float64")
        df2_expected = df2

        functions = [
            lambda x: x.expanding().count(),
            lambda x: x.expanding(min_periods=5).cov(x, pairwise=False),
            lambda x: x.expanding(min_periods=5).corr(x, pairwise=False),
            lambda x: x.expanding(min_periods=5).max(),
            lambda x: x.expanding(min_periods=5).min(),
            lambda x: x.expanding(min_periods=5).sum(),
            lambda x: x.expanding(min_periods=5).mean(),
            lambda x: x.expanding(min_periods=5).std(),
            lambda x: x.expanding(min_periods=5).var(),
            lambda x: x.expanding(min_periods=5).skew(),
            lambda x: x.expanding(min_periods=5).kurt(),
            lambda x: x.expanding(min_periods=5).quantile(0.5),
            lambda x: x.expanding(min_periods=5).median(),
            lambda x: x.expanding(min_periods=5).apply(sum, raw=False),
            lambda x: x.expanding(min_periods=5).apply(sum, raw=True),
            lambda x: x.rolling(window=10).count(),
            lambda x: x.rolling(window=10, min_periods=5).cov(x, pairwise=False),
            lambda x: x.rolling(window=10, min_periods=5).corr(x, pairwise=False),
            lambda x: x.rolling(window=10, min_periods=5).max(),
            lambda x: x.rolling(window=10, min_periods=5).min(),
            lambda x: x.rolling(window=10, min_periods=5).sum(),
            lambda x: x.rolling(window=10, min_periods=5).mean(),
            lambda x: x.rolling(window=10, min_periods=5).std(),
            lambda x: x.rolling(window=10, min_periods=5).var(),
            lambda x: x.rolling(window=10, min_periods=5).skew(),
            lambda x: x.rolling(window=10, min_periods=5).kurt(),
            lambda x: x.rolling(window=10, min_periods=5).quantile(0.5),
            lambda x: x.rolling(window=10, min_periods=5).median(),
            lambda x: x.rolling(window=10, min_periods=5).apply(sum, raw=False),
            lambda x: x.rolling(window=10, min_periods=5).apply(sum, raw=True),
            lambda x: x.rolling(win_type="boxcar", window=10, min_periods=5).mean(),
        ]
        for f in functions:
            try:
                s_result = f(s)
                tm.assert_series_equal(s_result, s_expected)

                df1_result = f(df1)
                tm.assert_frame_equal(df1_result, df1_expected)

                df2_result = f(df2)
                tm.assert_frame_equal(df2_result, df2_expected)
            except (ImportError):

                # scipy needed for rolling_window
                continue

    def test_moment_functions_zero_length_pairwise(self):

        df1 = DataFrame()
        df1_expected = df1
        df2 = DataFrame(columns=Index(["a"], name="foo"), index=Index([], name="bar"))
        df2["a"] = df2["a"].astype("float64")

        df1_expected = DataFrame(
            index=pd.MultiIndex.from_product([df1.index, df1.columns]),
            columns=Index([]),
        )
        df2_expected = DataFrame(
            index=pd.MultiIndex.from_product(
                [df2.index, df2.columns], names=["bar", "foo"]
            ),
            columns=Index(["a"], name="foo"),
            dtype="float64",
        )

        functions = [
            lambda x: (x.expanding(min_periods=5).cov(x, pairwise=True)),
            lambda x: (x.expanding(min_periods=5).corr(x, pairwise=True)),
            lambda x: (x.rolling(window=10, min_periods=5).cov(x, pairwise=True)),
            lambda x: (x.rolling(window=10, min_periods=5).corr(x, pairwise=True)),
        ]
        for f in functions:
            df1_result = f(df1)
            tm.assert_frame_equal(df1_result, df1_expected)

            df2_result = f(df2)
            tm.assert_frame_equal(df2_result, df2_expected)

    def test_expanding_cov_pairwise_diff_length(self):
        # GH 7512
        df1 = DataFrame([[1, 5], [3, 2], [3, 9]], columns=Index(["A", "B"], name="foo"))
        df1a = DataFrame(
            [[1, 5], [3, 9]], index=[0, 2], columns=Index(["A", "B"], name="foo")
        )
        df2 = DataFrame(
            [[5, 6], [None, None], [2, 1]], columns=Index(["X", "Y"], name="foo")
        )
        df2a = DataFrame(
            [[5, 6], [2, 1]], index=[0, 2], columns=Index(["X", "Y"], name="foo")
        )
        # TODO: xref gh-15826
        # .loc is not preserving the names
        result1 = df1.expanding().cov(df2a, pairwise=True).loc[2]
        result2 = df1.expanding().cov(df2a, pairwise=True).loc[2]
        result3 = df1a.expanding().cov(df2, pairwise=True).loc[2]
        result4 = df1a.expanding().cov(df2a, pairwise=True).loc[2]
        expected = DataFrame(
            [[-3.0, -6.0], [-5.0, -10.0]],
            columns=Index(["A", "B"], name="foo"),
            index=Index(["X", "Y"], name="foo"),
        )
        tm.assert_frame_equal(result1, expected)
        tm.assert_frame_equal(result2, expected)
        tm.assert_frame_equal(result3, expected)
        tm.assert_frame_equal(result4, expected)

    def test_expanding_corr_pairwise_diff_length(self):
        # GH 7512
        df1 = DataFrame(
            [[1, 2], [3, 2], [3, 4]],
            columns=["A", "B"],
            index=Index(range(3), name="bar"),
        )
        df1a = DataFrame(
            [[1, 2], [3, 4]], index=Index([0, 2], name="bar"), columns=["A", "B"]
        )
        df2 = DataFrame(
            [[5, 6], [None, None], [2, 1]],
            columns=["X", "Y"],
            index=Index(range(3), name="bar"),
        )
        df2a = DataFrame(
            [[5, 6], [2, 1]], index=Index([0, 2], name="bar"), columns=["X", "Y"]
        )
        result1 = df1.expanding().corr(df2, pairwise=True).loc[2]
        result2 = df1.expanding().corr(df2a, pairwise=True).loc[2]
        result3 = df1a.expanding().corr(df2, pairwise=True).loc[2]
        result4 = df1a.expanding().corr(df2a, pairwise=True).loc[2]
        expected = DataFrame(
            [[-1.0, -1.0], [-1.0, -1.0]], columns=["A", "B"], index=Index(["X", "Y"])
        )
        tm.assert_frame_equal(result1, expected)
        tm.assert_frame_equal(result2, expected)
        tm.assert_frame_equal(result3, expected)
        tm.assert_frame_equal(result4, expected)

    def test_rolling_skew_edge_cases(self):

        all_nan = Series([np.NaN] * 5)

        # yields all NaN (0 variance)
        d = Series([1] * 5)
        x = d.rolling(window=5).skew()
        tm.assert_series_equal(all_nan, x)

        # yields all NaN (window too small)
        d = Series(np.random.randn(5))
        x = d.rolling(window=2).skew()
        tm.assert_series_equal(all_nan, x)

        # yields [NaN, NaN, NaN, 0.177994, 1.548824]
        d = Series([-1.50837035, -0.1297039, 0.19501095, 1.73508164, 0.41941401])
        expected = Series([np.NaN, np.NaN, np.NaN, 0.177994, 1.548824])
        x = d.rolling(window=4).skew()
        tm.assert_series_equal(expected, x)

    def test_rolling_kurt_edge_cases(self):

        all_nan = Series([np.NaN] * 5)

        # yields all NaN (0 variance)
        d = Series([1] * 5)
        x = d.rolling(window=5).kurt()
        tm.assert_series_equal(all_nan, x)

        # yields all NaN (window too small)
        d = Series(np.random.randn(5))
        x = d.rolling(window=3).kurt()
        tm.assert_series_equal(all_nan, x)

        # yields [NaN, NaN, NaN, 1.224307, 2.671499]
        d = Series([-1.50837035, -0.1297039, 0.19501095, 1.73508164, 0.41941401])
        expected = Series([np.NaN, np.NaN, np.NaN, 1.224307, 2.671499])
        x = d.rolling(window=4).kurt()
        tm.assert_series_equal(expected, x)

    def test_rolling_skew_eq_value_fperr(self):
        # #18804 all rolling skew for all equal values should return Nan
        a = Series([1.1] * 15).rolling(window=10).skew()
        assert np.isnan(a).all()

    def test_rolling_kurt_eq_value_fperr(self):
        # #18804 all rolling kurt for all equal values should return Nan
        a = Series([1.1] * 15).rolling(window=10).kurt()
        assert np.isnan(a).all()

    @pytest.mark.parametrize(
        "func,static_comp",
        [("sum", np.sum), ("mean", np.mean), ("max", np.max), ("min", np.min)],
        ids=["sum", "mean", "max", "min"],
    )
    def test_expanding_func(self, func, static_comp):
        def expanding_func(x, min_periods=1, center=False, axis=0):
            exp = x.expanding(min_periods=min_periods, center=center, axis=axis)
            return getattr(exp, func)()

        self._check_expanding(expanding_func, static_comp, preserve_nan=False)

    def test_expanding_apply(self, raw):
        def expanding_mean(x, min_periods=1):

            exp = x.expanding(min_periods=min_periods)
            result = exp.apply(lambda x: x.mean(), raw=raw)
            return result

        # TODO(jreback), needed to add preserve_nan=False
        # here to make this pass
        self._check_expanding(expanding_mean, np.mean, preserve_nan=False)

        ser = Series([])
        tm.assert_series_equal(ser, ser.expanding().apply(lambda x: x.mean(), raw=raw))

        # GH 8080
        s = Series([None, None, None])
        result = s.expanding(min_periods=0).apply(lambda x: len(x), raw=raw)
        expected = Series([1.0, 2.0, 3.0])
        tm.assert_series_equal(result, expected)

    def _check_expanding(
        self,
        func,
        static_comp,
        has_min_periods=True,
        has_time_rule=True,
        preserve_nan=True,
    ):

        series_result = func(self.series)
        assert isinstance(series_result, Series)
        frame_result = func(self.frame)
        assert isinstance(frame_result, DataFrame)

        result = func(self.series)
        tm.assert_almost_equal(result[10], static_comp(self.series[:11]))

        if preserve_nan:
            assert result.iloc[self._nan_locs].isna().all()

        ser = Series(randn(50))

        if has_min_periods:
            result = func(ser, min_periods=30)
            assert result[:29].isna().all()
            tm.assert_almost_equal(result.iloc[-1], static_comp(ser[:50]))

            # min_periods is working correctly
            result = func(ser, min_periods=15)
            assert isna(result.iloc[13])
            assert notna(result.iloc[14])

            ser2 = Series(randn(20))
            result = func(ser2, min_periods=5)
            assert isna(result[3])
            assert notna(result[4])

            # min_periods=0
            result0 = func(ser, min_periods=0)
            result1 = func(ser, min_periods=1)
            tm.assert_almost_equal(result0, result1)
        else:
            result = func(ser)
            tm.assert_almost_equal(result.iloc[-1], static_comp(ser[:50]))

    def test_rolling_max_gh6297(self):
        """Replicate result expected in GH #6297"""

        indices = [datetime(1975, 1, i) for i in range(1, 6)]
        # So that we can have 2 datapoints on one of the days
        indices.append(datetime(1975, 1, 3, 6, 0))
        series = Series(range(1, 7), index=indices)
        # Use floats instead of ints as values
        series = series.map(lambda x: float(x))
        # Sort chronologically
        series = series.sort_index()

        expected = Series(
            [1.0, 2.0, 6.0, 4.0, 5.0],
            index=[datetime(1975, 1, i, 0) for i in range(1, 6)],
        )
        x = series.resample("D").max().rolling(window=1).max()
        tm.assert_series_equal(expected, x)

    def test_rolling_max_resample(self):

        indices = [datetime(1975, 1, i) for i in range(1, 6)]
        # So that we can have 3 datapoints on last day (4, 10, and 20)
        indices.append(datetime(1975, 1, 5, 1))
        indices.append(datetime(1975, 1, 5, 2))
        series = Series(list(range(0, 5)) + [10, 20], index=indices)
        # Use floats instead of ints as values
        series = series.map(lambda x: float(x))
        # Sort chronologically
        series = series.sort_index()

        # Default how should be max
        expected = Series(
            [0.0, 1.0, 2.0, 3.0, 20.0],
            index=[datetime(1975, 1, i, 0) for i in range(1, 6)],
        )
        x = series.resample("D").max().rolling(window=1).max()
        tm.assert_series_equal(expected, x)

        # Now specify median (10.0)
        expected = Series(
            [0.0, 1.0, 2.0, 3.0, 10.0],
            index=[datetime(1975, 1, i, 0) for i in range(1, 6)],
        )
        x = series.resample("D").median().rolling(window=1).max()
        tm.assert_series_equal(expected, x)

        # Now specify mean (4+10+20)/3
        v = (4.0 + 10.0 + 20.0) / 3.0
        expected = Series(
            [0.0, 1.0, 2.0, 3.0, v],
            index=[datetime(1975, 1, i, 0) for i in range(1, 6)],
        )
        x = series.resample("D").mean().rolling(window=1).max()
        tm.assert_series_equal(expected, x)

    def test_rolling_min_resample(self):

        indices = [datetime(1975, 1, i) for i in range(1, 6)]
        # So that we can have 3 datapoints on last day (4, 10, and 20)
        indices.append(datetime(1975, 1, 5, 1))
        indices.append(datetime(1975, 1, 5, 2))
        series = Series(list(range(0, 5)) + [10, 20], index=indices)
        # Use floats instead of ints as values
        series = series.map(lambda x: float(x))
        # Sort chronologically
        series = series.sort_index()

        # Default how should be min
        expected = Series(
            [0.0, 1.0, 2.0, 3.0, 4.0],
            index=[datetime(1975, 1, i, 0) for i in range(1, 6)],
        )
        r = series.resample("D").min().rolling(window=1)
        tm.assert_series_equal(expected, r.min())

    def test_rolling_median_resample(self):

        indices = [datetime(1975, 1, i) for i in range(1, 6)]
        # So that we can have 3 datapoints on last day (4, 10, and 20)
        indices.append(datetime(1975, 1, 5, 1))
        indices.append(datetime(1975, 1, 5, 2))
        series = Series(list(range(0, 5)) + [10, 20], index=indices)
        # Use floats instead of ints as values
        series = series.map(lambda x: float(x))
        # Sort chronologically
        series = series.sort_index()

        # Default how should be median
        expected = Series(
            [0.0, 1.0, 2.0, 3.0, 10],
            index=[datetime(1975, 1, i, 0) for i in range(1, 6)],
        )
        x = series.resample("D").median().rolling(window=1).median()
        tm.assert_series_equal(expected, x)

    def test_rolling_median_memory_error(self):
        # GH11722
        n = 20000
        Series(np.random.randn(n)).rolling(window=2, center=False).median()
        Series(np.random.randn(n)).rolling(window=2, center=False).median()

    def test_rolling_min_max_numeric_types(self):

        # GH12373
        types_test = [np.dtype("f{}".format(width)) for width in [4, 8]]
        types_test.extend(
            [
                np.dtype("{}{}".format(sign, width))
                for width in [1, 2, 4, 8]
                for sign in "ui"
            ]
        )
        for data_type in types_test:
            # Just testing that these don't throw exceptions and that
            # the return type is float64. Other tests will cover quantitative
            # correctness
            result = DataFrame(np.arange(20, dtype=data_type)).rolling(window=5).max()
            assert result.dtypes[0] == np.dtype("f8")
            result = DataFrame(np.arange(20, dtype=data_type)).rolling(window=5).min()
            assert result.dtypes[0] == np.dtype("f8")


class TestGrouperGrouping:
    def setup_method(self, method):
        self.series = Series(np.arange(10))
        self.frame = DataFrame({"A": [1] * 20 + [2] * 12 + [3] * 8, "B": np.arange(40)})

    def test_mutated(self):

        msg = r"group\(\) got an unexpected keyword argument 'foo'"
        with pytest.raises(TypeError, match=msg):
            self.frame.groupby("A", foo=1)

        g = self.frame.groupby("A")
        assert not g.mutated
        g = self.frame.groupby("A", mutated=True)
        assert g.mutated

    def test_getitem(self):
        g = self.frame.groupby("A")
        g_mutated = self.frame.groupby("A", mutated=True)

        expected = g_mutated.B.apply(lambda x: x.rolling(2).mean())

        result = g.rolling(2).mean().B
        tm.assert_series_equal(result, expected)

        result = g.rolling(2).B.mean()
        tm.assert_series_equal(result, expected)

        result = g.B.rolling(2).mean()
        tm.assert_series_equal(result, expected)

        result = self.frame.B.groupby(self.frame.A).rolling(2).mean()
        tm.assert_series_equal(result, expected)

    def test_getitem_multiple(self):

        # GH 13174
        g = self.frame.groupby("A")
        r = g.rolling(2)
        g_mutated = self.frame.groupby("A", mutated=True)
        expected = g_mutated.B.apply(lambda x: x.rolling(2).count())

        result = r.B.count()
        tm.assert_series_equal(result, expected)

        result = r.B.count()
        tm.assert_series_equal(result, expected)

    def test_rolling(self):
        g = self.frame.groupby("A")
        r = g.rolling(window=4)

        for f in ["sum", "mean", "min", "max", "count", "kurt", "skew"]:

            result = getattr(r, f)()
            expected = g.apply(lambda x: getattr(x.rolling(4), f)())
            tm.assert_frame_equal(result, expected)

        for f in ["std", "var"]:
            result = getattr(r, f)(ddof=1)
            expected = g.apply(lambda x: getattr(x.rolling(4), f)(ddof=1))
            tm.assert_frame_equal(result, expected)

        result = r.quantile(0.5)
        expected = g.apply(lambda x: x.rolling(4).quantile(0.5))
        tm.assert_frame_equal(result, expected)

    def test_rolling_corr_cov(self):
        g = self.frame.groupby("A")
        r = g.rolling(window=4)

        for f in ["corr", "cov"]:
            result = getattr(r, f)(self.frame)

            def func(x):
                return getattr(x.rolling(4), f)(self.frame)

            expected = g.apply(func)
            tm.assert_frame_equal(result, expected)

            result = getattr(r.B, f)(pairwise=True)

            def func(x):
                return getattr(x.B.rolling(4), f)(pairwise=True)

            expected = g.apply(func)
            tm.assert_series_equal(result, expected)

    def test_rolling_apply(self, raw):
        g = self.frame.groupby("A")
        r = g.rolling(window=4)

        # reduction
        result = r.apply(lambda x: x.sum(), raw=raw)
        expected = g.apply(lambda x: x.rolling(4).apply(lambda y: y.sum(), raw=raw))
        tm.assert_frame_equal(result, expected)

    def test_rolling_apply_mutability(self):
        # GH 14013
        df = pd.DataFrame({"A": ["foo"] * 3 + ["bar"] * 3, "B": [1] * 6})
        g = df.groupby("A")

        mi = pd.MultiIndex.from_tuples(
            [("bar", 3), ("bar", 4), ("bar", 5), ("foo", 0), ("foo", 1), ("foo", 2)]
        )

        mi.names = ["A", None]
        # Grouped column should not be a part of the output
        expected = pd.DataFrame([np.nan, 2.0, 2.0] * 2, columns=["B"], index=mi)

        result = g.rolling(window=2).sum()
        tm.assert_frame_equal(result, expected)

        # Call an arbitrary function on the groupby
        g.sum()

        # Make sure nothing has been mutated
        result = g.rolling(window=2).sum()
        tm.assert_frame_equal(result, expected)

    def test_expanding(self):
        g = self.frame.groupby("A")
        r = g.expanding()

        for f in ["sum", "mean", "min", "max", "count", "kurt", "skew"]:

            result = getattr(r, f)()
            expected = g.apply(lambda x: getattr(x.expanding(), f)())
            tm.assert_frame_equal(result, expected)

        for f in ["std", "var"]:
            result = getattr(r, f)(ddof=0)
            expected = g.apply(lambda x: getattr(x.expanding(), f)(ddof=0))
            tm.assert_frame_equal(result, expected)

        result = r.quantile(0.5)
        expected = g.apply(lambda x: x.expanding().quantile(0.5))
        tm.assert_frame_equal(result, expected)

    def test_expanding_corr_cov(self):
        g = self.frame.groupby("A")
        r = g.expanding()

        for f in ["corr", "cov"]:
            result = getattr(r, f)(self.frame)

            def func(x):
                return getattr(x.expanding(), f)(self.frame)

            expected = g.apply(func)
            tm.assert_frame_equal(result, expected)

            result = getattr(r.B, f)(pairwise=True)

            def func(x):
                return getattr(x.B.expanding(), f)(pairwise=True)

            expected = g.apply(func)
            tm.assert_series_equal(result, expected)

    def test_expanding_apply(self, raw):
        g = self.frame.groupby("A")
        r = g.expanding()

        # reduction
        result = r.apply(lambda x: x.sum(), raw=raw)
        expected = g.apply(lambda x: x.expanding().apply(lambda y: y.sum(), raw=raw))
        tm.assert_frame_equal(result, expected)


class TestRollingTS:

    # rolling time-series friendly
    # xref GH13327

    def setup_method(self, method):

        self.regular = DataFrame(
            {"A": pd.date_range("20130101", periods=5, freq="s"), "B": range(5)}
        ).set_index("A")

        self.ragged = DataFrame({"B": range(5)})
        self.ragged.index = [
            Timestamp("20130101 09:00:00"),
            Timestamp("20130101 09:00:02"),
            Timestamp("20130101 09:00:03"),
            Timestamp("20130101 09:00:05"),
            Timestamp("20130101 09:00:06"),
        ]

    def test_doc_string(self):

        df = DataFrame(
            {"B": [0, 1, 2, np.nan, 4]},
            index=[
                Timestamp("20130101 09:00:00"),
                Timestamp("20130101 09:00:02"),
                Timestamp("20130101 09:00:03"),
                Timestamp("20130101 09:00:05"),
                Timestamp("20130101 09:00:06"),
            ],
        )
        df
        df.rolling("2s").sum()

    def test_valid(self):

        df = self.regular

        # not a valid freq
        with pytest.raises(ValueError):
            df.rolling(window="foobar")

        # not a datetimelike index
        with pytest.raises(ValueError):
            df.reset_index().rolling(window="foobar")

        # non-fixed freqs
        for freq in ["2MS", pd.offsets.MonthBegin(2)]:
            with pytest.raises(ValueError):
                df.rolling(window=freq)

        for freq in ["1D", pd.offsets.Day(2), "2ms"]:
            df.rolling(window=freq)

        # non-integer min_periods
        for minp in [1.0, "foo", np.array([1, 2, 3])]:
            with pytest.raises(ValueError):
                df.rolling(window="1D", min_periods=minp)

        # center is not implemented
        with pytest.raises(NotImplementedError):
            df.rolling(window="1D", center=True)

    def test_on(self):

        df = self.regular

        # not a valid column
        with pytest.raises(ValueError):
            df.rolling(window="2s", on="foobar")

        # column is valid
        df = df.copy()
        df["C"] = pd.date_range("20130101", periods=len(df))
        df.rolling(window="2d", on="C").sum()

        # invalid columns
        with pytest.raises(ValueError):
            df.rolling(window="2d", on="B")

        # ok even though on non-selected
        df.rolling(window="2d", on="C").B.sum()

    def test_monotonic_on(self):

        # on/index must be monotonic
        df = DataFrame(
            {"A": pd.date_range("20130101", periods=5, freq="s"), "B": range(5)}
        )

        assert df.A.is_monotonic
        df.rolling("2s", on="A").sum()

        df = df.set_index("A")
        assert df.index.is_monotonic
        df.rolling("2s").sum()

        # non-monotonic
        df.index = reversed(df.index.tolist())
        assert not df.index.is_monotonic

        with pytest.raises(ValueError):
            df.rolling("2s").sum()

        df = df.reset_index()
        with pytest.raises(ValueError):
            df.rolling("2s", on="A").sum()

    def test_frame_on(self):

        df = DataFrame(
            {
                "B": range(5),
                "C": pd.date_range("20130101 09:00:00", periods=5, freq="3s"),
            }
        )

        df["A"] = [
            Timestamp("20130101 09:00:00"),
            Timestamp("20130101 09:00:02"),
            Timestamp("20130101 09:00:03"),
            Timestamp("20130101 09:00:05"),
            Timestamp("20130101 09:00:06"),
        ]

        # we are doing simulating using 'on'
        expected = df.set_index("A").rolling("2s").B.sum().reset_index(drop=True)

        result = df.rolling("2s", on="A").B.sum()
        tm.assert_series_equal(result, expected)

        # test as a frame
        # we should be ignoring the 'on' as an aggregation column
        # note that the expected is setting, computing, and resetting
        # so the columns need to be switched compared
        # to the actual result where they are ordered as in the
        # original
        expected = (
            df.set_index("A").rolling("2s")[["B"]].sum().reset_index()[["B", "A"]]
        )

        result = df.rolling("2s", on="A")[["B"]].sum()
        tm.assert_frame_equal(result, expected)

    def test_frame_on2(self):

        # using multiple aggregation columns
        df = DataFrame(
            {
                "A": [0, 1, 2, 3, 4],
                "B": [0, 1, 2, np.nan, 4],
                "C": Index(
                    [
                        Timestamp("20130101 09:00:00"),
                        Timestamp("20130101 09:00:02"),
                        Timestamp("20130101 09:00:03"),
                        Timestamp("20130101 09:00:05"),
                        Timestamp("20130101 09:00:06"),
                    ]
                ),
            },
            columns=["A", "C", "B"],
        )

        expected1 = DataFrame(
            {"A": [0.0, 1, 3, 3, 7], "B": [0, 1, 3, np.nan, 4], "C": df["C"]},
            columns=["A", "C", "B"],
        )

        result = df.rolling("2s", on="C").sum()
        expected = expected1
        tm.assert_frame_equal(result, expected)

        expected = Series([0, 1, 3, np.nan, 4], name="B")
        result = df.rolling("2s", on="C").B.sum()
        tm.assert_series_equal(result, expected)

        expected = expected1[["A", "B", "C"]]
        result = df.rolling("2s", on="C")[["A", "B", "C"]].sum()
        tm.assert_frame_equal(result, expected)

    def test_basic_regular(self):

        df = self.regular.copy()

        df.index = pd.date_range("20130101", periods=5, freq="D")
        expected = df.rolling(window=1, min_periods=1).sum()
        result = df.rolling(window="1D").sum()
        tm.assert_frame_equal(result, expected)

        df.index = pd.date_range("20130101", periods=5, freq="2D")
        expected = df.rolling(window=1, min_periods=1).sum()
        result = df.rolling(window="2D", min_periods=1).sum()
        tm.assert_frame_equal(result, expected)

        expected = df.rolling(window=1, min_periods=1).sum()
        result = df.rolling(window="2D", min_periods=1).sum()
        tm.assert_frame_equal(result, expected)

        expected = df.rolling(window=1).sum()
        result = df.rolling(window="2D").sum()
        tm.assert_frame_equal(result, expected)

    def test_min_periods(self):

        # compare for min_periods
        df = self.regular

        # these slightly different
        expected = df.rolling(2, min_periods=1).sum()
        result = df.rolling("2s").sum()
        tm.assert_frame_equal(result, expected)

        expected = df.rolling(2, min_periods=1).sum()
        result = df.rolling("2s", min_periods=1).sum()
        tm.assert_frame_equal(result, expected)

    def test_closed(self):

        # xref GH13965

        df = DataFrame(
            {"A": [1] * 5},
            index=[
                Timestamp("20130101 09:00:01"),
                Timestamp("20130101 09:00:02"),
                Timestamp("20130101 09:00:03"),
                Timestamp("20130101 09:00:04"),
                Timestamp("20130101 09:00:06"),
            ],
        )

        # closed must be 'right', 'left', 'both', 'neither'
        with pytest.raises(ValueError):
            self.regular.rolling(window="2s", closed="blabla")

        expected = df.copy()
        expected["A"] = [1.0, 2, 2, 2, 1]
        result = df.rolling("2s", closed="right").sum()
        tm.assert_frame_equal(result, expected)

        # default should be 'right'
        result = df.rolling("2s").sum()
        tm.assert_frame_equal(result, expected)

        expected = df.copy()
        expected["A"] = [1.0, 2, 3, 3, 2]
        result = df.rolling("2s", closed="both").sum()
        tm.assert_frame_equal(result, expected)

        expected = df.copy()
        expected["A"] = [np.nan, 1.0, 2, 2, 1]
        result = df.rolling("2s", closed="left").sum()
        tm.assert_frame_equal(result, expected)

        expected = df.copy()
        expected["A"] = [np.nan, 1.0, 1, 1, np.nan]
        result = df.rolling("2s", closed="neither").sum()
        tm.assert_frame_equal(result, expected)

    def test_ragged_sum(self):

        df = self.ragged
        result = df.rolling(window="1s", min_periods=1).sum()
        expected = df.copy()
        expected["B"] = [0.0, 1, 2, 3, 4]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="2s", min_periods=1).sum()
        expected = df.copy()
        expected["B"] = [0.0, 1, 3, 3, 7]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="2s", min_periods=2).sum()
        expected = df.copy()
        expected["B"] = [np.nan, np.nan, 3, np.nan, 7]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="3s", min_periods=1).sum()
        expected = df.copy()
        expected["B"] = [0.0, 1, 3, 5, 7]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="3s").sum()
        expected = df.copy()
        expected["B"] = [0.0, 1, 3, 5, 7]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="4s", min_periods=1).sum()
        expected = df.copy()
        expected["B"] = [0.0, 1, 3, 6, 9]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="4s", min_periods=3).sum()
        expected = df.copy()
        expected["B"] = [np.nan, np.nan, 3, 6, 9]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="5s", min_periods=1).sum()
        expected = df.copy()
        expected["B"] = [0.0, 1, 3, 6, 10]
        tm.assert_frame_equal(result, expected)

    def test_ragged_mean(self):

        df = self.ragged
        result = df.rolling(window="1s", min_periods=1).mean()
        expected = df.copy()
        expected["B"] = [0.0, 1, 2, 3, 4]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="2s", min_periods=1).mean()
        expected = df.copy()
        expected["B"] = [0.0, 1, 1.5, 3.0, 3.5]
        tm.assert_frame_equal(result, expected)

    def test_ragged_median(self):

        df = self.ragged
        result = df.rolling(window="1s", min_periods=1).median()
        expected = df.copy()
        expected["B"] = [0.0, 1, 2, 3, 4]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="2s", min_periods=1).median()
        expected = df.copy()
        expected["B"] = [0.0, 1, 1.5, 3.0, 3.5]
        tm.assert_frame_equal(result, expected)

    def test_ragged_quantile(self):

        df = self.ragged
        result = df.rolling(window="1s", min_periods=1).quantile(0.5)
        expected = df.copy()
        expected["B"] = [0.0, 1, 2, 3, 4]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="2s", min_periods=1).quantile(0.5)
        expected = df.copy()
        expected["B"] = [0.0, 1, 1.5, 3.0, 3.5]
        tm.assert_frame_equal(result, expected)

    def test_ragged_std(self):

        df = self.ragged
        result = df.rolling(window="1s", min_periods=1).std(ddof=0)
        expected = df.copy()
        expected["B"] = [0.0] * 5
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="1s", min_periods=1).std(ddof=1)
        expected = df.copy()
        expected["B"] = [np.nan] * 5
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="3s", min_periods=1).std(ddof=0)
        expected = df.copy()
        expected["B"] = [0.0] + [0.5] * 4
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="5s", min_periods=1).std(ddof=1)
        expected = df.copy()
        expected["B"] = [np.nan, 0.707107, 1.0, 1.0, 1.290994]
        tm.assert_frame_equal(result, expected)

    def test_ragged_var(self):

        df = self.ragged
        result = df.rolling(window="1s", min_periods=1).var(ddof=0)
        expected = df.copy()
        expected["B"] = [0.0] * 5
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="1s", min_periods=1).var(ddof=1)
        expected = df.copy()
        expected["B"] = [np.nan] * 5
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="3s", min_periods=1).var(ddof=0)
        expected = df.copy()
        expected["B"] = [0.0] + [0.25] * 4
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="5s", min_periods=1).var(ddof=1)
        expected = df.copy()
        expected["B"] = [np.nan, 0.5, 1.0, 1.0, 1 + 2 / 3.0]
        tm.assert_frame_equal(result, expected)

    def test_ragged_skew(self):

        df = self.ragged
        result = df.rolling(window="3s", min_periods=1).skew()
        expected = df.copy()
        expected["B"] = [np.nan] * 5
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="5s", min_periods=1).skew()
        expected = df.copy()
        expected["B"] = [np.nan] * 2 + [0.0, 0.0, 0.0]
        tm.assert_frame_equal(result, expected)

    def test_ragged_kurt(self):

        df = self.ragged
        result = df.rolling(window="3s", min_periods=1).kurt()
        expected = df.copy()
        expected["B"] = [np.nan] * 5
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="5s", min_periods=1).kurt()
        expected = df.copy()
        expected["B"] = [np.nan] * 4 + [-1.2]
        tm.assert_frame_equal(result, expected)

    def test_ragged_count(self):

        df = self.ragged
        result = df.rolling(window="1s", min_periods=1).count()
        expected = df.copy()
        expected["B"] = [1.0, 1, 1, 1, 1]
        tm.assert_frame_equal(result, expected)

        df = self.ragged
        result = df.rolling(window="1s").count()
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="2s", min_periods=1).count()
        expected = df.copy()
        expected["B"] = [1.0, 1, 2, 1, 2]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="2s", min_periods=2).count()
        expected = df.copy()
        expected["B"] = [np.nan, np.nan, 2, np.nan, 2]
        tm.assert_frame_equal(result, expected)

    def test_regular_min(self):

        df = DataFrame(
            {
                "A": pd.date_range("20130101", periods=5, freq="s"),
                "B": [0.0, 1, 2, 3, 4],
            }
        ).set_index("A")
        result = df.rolling("1s").min()
        expected = df.copy()
        expected["B"] = [0.0, 1, 2, 3, 4]
        tm.assert_frame_equal(result, expected)

        df = DataFrame(
            {"A": pd.date_range("20130101", periods=5, freq="s"), "B": [5, 4, 3, 4, 5]}
        ).set_index("A")

        tm.assert_frame_equal(result, expected)
        result = df.rolling("2s").min()
        expected = df.copy()
        expected["B"] = [5.0, 4, 3, 3, 4]
        tm.assert_frame_equal(result, expected)

        result = df.rolling("5s").min()
        expected = df.copy()
        expected["B"] = [5.0, 4, 3, 3, 3]
        tm.assert_frame_equal(result, expected)

    def test_ragged_min(self):

        df = self.ragged

        result = df.rolling(window="1s", min_periods=1).min()
        expected = df.copy()
        expected["B"] = [0.0, 1, 2, 3, 4]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="2s", min_periods=1).min()
        expected = df.copy()
        expected["B"] = [0.0, 1, 1, 3, 3]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="5s", min_periods=1).min()
        expected = df.copy()
        expected["B"] = [0.0, 0, 0, 1, 1]
        tm.assert_frame_equal(result, expected)

    def test_perf_min(self):

        N = 10000

        dfp = DataFrame(
            {"B": np.random.randn(N)},
            index=pd.date_range("20130101", periods=N, freq="s"),
        )
        expected = dfp.rolling(2, min_periods=1).min()
        result = dfp.rolling("2s").min()
        assert ((result - expected) < 0.01).all().bool()

        expected = dfp.rolling(200, min_periods=1).min()
        result = dfp.rolling("200s").min()
        assert ((result - expected) < 0.01).all().bool()

    def test_ragged_max(self):

        df = self.ragged

        result = df.rolling(window="1s", min_periods=1).max()
        expected = df.copy()
        expected["B"] = [0.0, 1, 2, 3, 4]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="2s", min_periods=1).max()
        expected = df.copy()
        expected["B"] = [0.0, 1, 2, 3, 4]
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="5s", min_periods=1).max()
        expected = df.copy()
        expected["B"] = [0.0, 1, 2, 3, 4]
        tm.assert_frame_equal(result, expected)

    def test_ragged_apply(self, raw):

        df = self.ragged

        f = lambda x: 1
        result = df.rolling(window="1s", min_periods=1).apply(f, raw=raw)
        expected = df.copy()
        expected["B"] = 1.0
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="2s", min_periods=1).apply(f, raw=raw)
        expected = df.copy()
        expected["B"] = 1.0
        tm.assert_frame_equal(result, expected)

        result = df.rolling(window="5s", min_periods=1).apply(f, raw=raw)
        expected = df.copy()
        expected["B"] = 1.0
        tm.assert_frame_equal(result, expected)

    def test_all(self):

        # simple comparison of integer vs time-based windowing
        df = self.regular * 2
        er = df.rolling(window=1)
        r = df.rolling(window="1s")

        for f in [
            "sum",
            "mean",
            "count",
            "median",
            "std",
            "var",
            "kurt",
            "skew",
            "min",
            "max",
        ]:

            result = getattr(r, f)()
            expected = getattr(er, f)()
            tm.assert_frame_equal(result, expected)

        result = r.quantile(0.5)
        expected = er.quantile(0.5)
        tm.assert_frame_equal(result, expected)

    def test_all_apply(self, raw):

        df = self.regular * 2
        er = df.rolling(window=1)
        r = df.rolling(window="1s")

        result = r.apply(lambda x: 1, raw=raw)
        expected = er.apply(lambda x: 1, raw=raw)
        tm.assert_frame_equal(result, expected)

    def test_all2(self):

        # more sophisticated comparison of integer vs.
        # time-based windowing
        df = DataFrame(
            {"B": np.arange(50)}, index=pd.date_range("20130101", periods=50, freq="H")
        )
        # in-range data
        dft = df.between_time("09:00", "16:00")

        r = dft.rolling(window="5H")

        for f in [
            "sum",
            "mean",
            "count",
            "median",
            "std",
            "var",
            "kurt",
            "skew",
            "min",
            "max",
        ]:

            result = getattr(r, f)()

            # we need to roll the days separately
            # to compare with a time-based roll
            # finally groupby-apply will return a multi-index
            # so we need to drop the day
            def agg_by_day(x):
                x = x.between_time("09:00", "16:00")
                return getattr(x.rolling(5, min_periods=1), f)()

            expected = (
                df.groupby(df.index.day)
                .apply(agg_by_day)
                .reset_index(level=0, drop=True)
            )

            tm.assert_frame_equal(result, expected)

    def test_groupby_monotonic(self):

        # GH 15130
        # we don't need to validate monotonicity when grouping

        data = [
            ["David", "1/1/2015", 100],
            ["David", "1/5/2015", 500],
            ["David", "5/30/2015", 50],
            ["David", "7/25/2015", 50],
            ["Ryan", "1/4/2014", 100],
            ["Ryan", "1/19/2015", 500],
            ["Ryan", "3/31/2016", 50],
            ["Joe", "7/1/2015", 100],
            ["Joe", "9/9/2015", 500],
            ["Joe", "10/15/2015", 50],
        ]

        df = DataFrame(data=data, columns=["name", "date", "amount"])
        df["date"] = pd.to_datetime(df["date"])

        expected = (
            df.set_index("date")
            .groupby("name")
            .apply(lambda x: x.rolling("180D")["amount"].sum())
        )
        result = df.groupby("name").rolling("180D", on="date")["amount"].sum()
        tm.assert_series_equal(result, expected)

    def test_non_monotonic(self):
        # GH 13966 (similar to #15130, closed by #15175)

        dates = pd.date_range(start="2016-01-01 09:30:00", periods=20, freq="s")
        df = DataFrame(
            {
                "A": [1] * 20 + [2] * 12 + [3] * 8,
                "B": np.concatenate((dates, dates)),
                "C": np.arange(40),
            }
        )

        result = df.groupby("A").rolling("4s", on="B").C.mean()
        expected = (
            df.set_index("B").groupby("A").apply(lambda x: x.rolling("4s")["C"].mean())
        )
        tm.assert_series_equal(result, expected)

        df2 = df.sort_values("B")
        result = df2.groupby("A").rolling("4s", on="B").C.mean()
        tm.assert_series_equal(result, expected)

    def test_rolling_cov_offset(self):
        # GH16058

        idx = pd.date_range("2017-01-01", periods=24, freq="1h")
        ss = Series(np.arange(len(idx)), index=idx)

        result = ss.rolling("2h").cov()
        expected = Series([np.nan] + [0.5] * (len(idx) - 1), index=idx)
        tm.assert_series_equal(result, expected)

        expected2 = ss.rolling(2, min_periods=1).cov()
        tm.assert_series_equal(result, expected2)

        result = ss.rolling("3h").cov()
        expected = Series([np.nan, 0.5] + [1.0] * (len(idx) - 2), index=idx)
        tm.assert_series_equal(result, expected)

        expected2 = ss.rolling(3, min_periods=1).cov()
        tm.assert_series_equal(result, expected2)