test_frame_value_counts.py

import numpy as np
import pytest

from pandas import (
    CategoricalIndex,
    DataFrame,
    Index,
    MultiIndex,
    Series,
)
import pandas._testing as tm


@pytest.fixture
def education_df():
    return DataFrame(
        {
            "gender": ["male", "male", "female", "male", "female", "male"],
            "education": ["low", "medium", "high", "low", "high", "low"],
            "country": ["US", "FR", "US", "FR", "FR", "FR"],
        }
    )


def test_axis(education_df):
    gp = education_df.groupby("country", axis=1)
    with pytest.raises(NotImplementedError, match="axis"):
        gp.value_counts()


def test_bad_subset(education_df):
    gp = education_df.groupby("country")
    with pytest.raises(ValueError, match="subset"):
        gp.value_counts(subset=["country"])


def test_basic(education_df):
    # gh43564
    result = education_df.groupby("country")[["gender", "education"]].value_counts(
        normalize=True
    )
    expected = Series(
        data=[0.5, 0.25, 0.25, 0.5, 0.5],
        index=MultiIndex.from_tuples(
            [
                ("FR", "male", "low"),
                ("FR", "female", "high"),
                ("FR", "male", "medium"),
                ("US", "female", "high"),
                ("US", "male", "low"),
            ],
            names=["country", "gender", "education"],
        ),
    )
    tm.assert_series_equal(result, expected)


def _frame_value_counts(df, keys, normalize, sort, ascending):
    return df[keys].value_counts(normalize=normalize, sort=sort, ascending=ascending)


@pytest.mark.parametrize("groupby", ["column", "array", "function"])
@pytest.mark.parametrize("normalize", [True, False])
@pytest.mark.parametrize(
    "sort, ascending",
    [
        (False, None),
        (True, True),
        (True, False),
    ],
)
@pytest.mark.parametrize("as_index", [True, False])
@pytest.mark.parametrize("frame", [True, False])
def test_against_frame_and_seriesgroupby(
    education_df, groupby, normalize, sort, ascending, as_index, frame
):
    # test all parameters:
    # - Use column, array or function as by= parameter
    # - Whether or not to normalize
    # - Whether or not to sort and how
    # - Whether or not to use the groupby as an index
    # - 3-way compare against:
    #   - apply with :meth:`~DataFrame.value_counts`
    #   - `~SeriesGroupBy.value_counts`
    by = {
        "column": "country",
        "array": education_df["country"].values,
        "function": lambda x: education_df["country"][x] == "US",
    }[groupby]

    gp = education_df.groupby(by=by, as_index=as_index)
    result = gp[["gender", "education"]].value_counts(
        normalize=normalize, sort=sort, ascending=ascending
    )
    if frame:
        # compare against apply with DataFrame value_counts
        expected = gp.apply(
            _frame_value_counts, ["gender", "education"], normalize, sort, ascending
        )

        if as_index:
            tm.assert_series_equal(result, expected)
        else:
            name = "proportion" if normalize else "count"
            expected = expected.reset_index().rename({0: name}, axis=1)
            if groupby == "column":
                expected = expected.rename({"level_0": "country"}, axis=1)
                expected["country"] = np.where(expected["country"], "US", "FR")
            elif groupby == "function":
                expected["level_0"] = expected["level_0"] == 1
            else:
                expected["level_0"] = np.where(expected["level_0"], "US", "FR")
            tm.assert_frame_equal(result, expected)
    else:
        # compare against SeriesGroupBy value_counts
        education_df["both"] = education_df["gender"] + "-" + education_df["education"]
        expected = gp["both"].value_counts(
            normalize=normalize, sort=sort, ascending=ascending
        )
        expected.name = None
        if as_index:
            index_frame = expected.index.to_frame(index=False)
            index_frame["gender"] = index_frame["both"].str.split("-").str.get(0)
            index_frame["education"] = index_frame["both"].str.split("-").str.get(1)
            del index_frame["both"]
            index_frame = index_frame.rename({0: None}, axis=1)
            expected.index = MultiIndex.from_frame(index_frame)
            tm.assert_series_equal(result, expected)
        else:
            expected.insert(1, "gender", expected["both"].str.split("-").str.get(0))
            expected.insert(2, "education", expected["both"].str.split("-").str.get(1))
            del expected["both"]
            tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize("normalize", [True, False])
@pytest.mark.parametrize(
    "sort, ascending, expected_rows, expected_count, expected_group_size",
    [
        (False, None, [0, 1, 2, 3, 4], [1, 1, 1, 2, 1], [1, 3, 1, 3, 1]),
        (True, False, [4, 3, 1, 2, 0], [1, 2, 1, 1, 1], [1, 3, 3, 1, 1]),
        (True, True, [4, 1, 3, 2, 0], [1, 1, 2, 1, 1], [1, 3, 3, 1, 1]),
    ],
)
def test_compound(
    education_df,
    normalize,
    sort,
    ascending,
    expected_rows,
    expected_count,
    expected_group_size,
):
    # Multiple groupby keys and as_index=False
    gp = education_df.groupby(["country", "gender"], as_index=False, sort=False)
    result = gp["education"].value_counts(
        normalize=normalize, sort=sort, ascending=ascending
    )
    expected = DataFrame()
    for column in ["country", "gender", "education"]:
        expected[column] = [education_df[column][row] for row in expected_rows]
    if normalize:
        expected["proportion"] = expected_count
        expected["proportion"] /= expected_group_size
    else:
        expected["count"] = expected_count
    tm.assert_frame_equal(result, expected)


@pytest.fixture
def animals_df():
    return DataFrame(
        {"key": [1, 1, 1, 1], "num_legs": [2, 4, 4, 6], "num_wings": [2, 0, 0, 0]},
        index=["falcon", "dog", "cat", "ant"],
    )


@pytest.mark.parametrize(
    "sort, ascending, normalize, expected_data, expected_index",
    [
        (False, None, False, [1, 2, 1], [(1, 1, 1), (2, 4, 6), (2, 0, 0)]),
        (True, True, False, [1, 1, 2], [(1, 1, 1), (2, 6, 4), (2, 0, 0)]),
        (True, False, False, [2, 1, 1], [(1, 1, 1), (4, 2, 6), (0, 2, 0)]),
        (True, False, True, [0.5, 0.25, 0.25], [(1, 1, 1), (4, 2, 6), (0, 2, 0)]),
    ],
)
def test_data_frame_value_counts(
    animals_df, sort, ascending, normalize, expected_data, expected_index
):
    # 3-way compare with :meth:`~DataFrame.value_counts`
    # Tests from frame/methods/test_value_counts.py
    result_frame = animals_df.value_counts(
        sort=sort, ascending=ascending, normalize=normalize
    )
    expected = Series(
        data=expected_data,
        index=MultiIndex.from_arrays(
            expected_index, names=["key", "num_legs", "num_wings"]
        ),
    )
    tm.assert_series_equal(result_frame, expected)

    result_frame_groupby = animals_df.groupby("key").value_counts(
        sort=sort, ascending=ascending, normalize=normalize
    )

    tm.assert_series_equal(result_frame_groupby, expected)


@pytest.fixture
def nulls_df():
    n = np.nan
    return DataFrame(
        {
            "A": [1, 1, n, 4, n, 6, 6, 6, 6],
            "B": [1, 1, 3, n, n, 6, 6, 6, 6],
            "C": [1, 2, 3, 4, 5, 6, n, 8, n],
            "D": [1, 2, 3, 4, 5, 6, 7, n, n],
        }
    )


@pytest.mark.parametrize(
    "group_dropna, count_dropna, expected_rows, expected_values",
    [
        (
            False,
            False,
            [0, 1, 3, 5, 7, 6, 8, 2, 4],
            [0.5, 0.5, 1.0, 0.25, 0.25, 0.25, 0.25, 1.0, 1.0],
        ),
        (False, True, [0, 1, 3, 5, 2, 4], [0.5, 0.5, 1.0, 1.0, 1.0, 1.0]),
        (True, False, [0, 1, 5, 7, 6, 8], [0.5, 0.5, 0.25, 0.25, 0.25, 0.25]),
        (True, True, [0, 1, 5], [0.5, 0.5, 1.0]),
    ],
)
def test_dropna_combinations(
    nulls_df, group_dropna, count_dropna, expected_rows, expected_values
):
    gp = nulls_df.groupby(["A", "B"], dropna=group_dropna)
    result = gp.value_counts(normalize=True, sort=True, dropna=count_dropna)
    columns = DataFrame()
    for column in nulls_df.columns:
        columns[column] = [nulls_df[column][row] for row in expected_rows]
    index = MultiIndex.from_frame(columns)
    expected = Series(data=expected_values, index=index)
    tm.assert_series_equal(result, expected)


@pytest.fixture
def names_with_nulls_df(nulls_fixture):
    return DataFrame(
        {
            "key": [1, 1, 1, 1],
            "first_name": ["John", "Anne", "John", "Beth"],
            "middle_name": ["Smith", nulls_fixture, nulls_fixture, "Louise"],
        },
    )


@pytest.mark.parametrize(
    "dropna, expected_data, expected_index",
    [
        (
            True,
            [1, 1],
            MultiIndex.from_arrays(
                [(1, 1), ("Beth", "John"), ("Louise", "Smith")],
                names=["key", "first_name", "middle_name"],
            ),
        ),
        (
            False,
            [1, 1, 1, 1],
            MultiIndex(
                levels=[
                    Index([1]),
                    Index(["Anne", "Beth", "John"]),
                    Index(["Louise", "Smith", np.nan]),
                ],
                codes=[[0, 0, 0, 0], [0, 1, 2, 2], [2, 0, 1, 2]],
                names=["key", "first_name", "middle_name"],
            ),
        ),
    ],
)
@pytest.mark.parametrize("normalize", [False, True])
def test_data_frame_value_counts_dropna(
    names_with_nulls_df, dropna, normalize, expected_data, expected_index
):
    # GH 41334
    # 3-way compare with :meth:`~DataFrame.value_counts`
    # Tests with nulls from frame/methods/test_value_counts.py
    result_frame = names_with_nulls_df.value_counts(dropna=dropna, normalize=normalize)
    expected = Series(
        data=expected_data,
        index=expected_index,
    )
    if normalize:
        expected /= float(len(expected_data))

    tm.assert_series_equal(result_frame, expected)

    result_frame_groupby = names_with_nulls_df.groupby("key").value_counts(
        dropna=dropna, normalize=normalize
    )

    tm.assert_series_equal(result_frame_groupby, expected)


@pytest.mark.parametrize("as_index", [False, True])
@pytest.mark.parametrize("observed", [False, True])
@pytest.mark.parametrize(
    "normalize, expected_data",
    [
        (False, np.array([2, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0], dtype=np.int64)),
        (
            True,
            np.array([0.5, 0.25, 0.25, 0.0, 0.0, 0.0, 0.5, 0.5, 0.0, 0.0, 0.0, 0.0]),
        ),
    ],
)
def test_categorical_single_grouper_with_only_observed_categories(
    education_df, as_index, observed, normalize, expected_data
):

    # Test single categorical grouper with only observed grouping categories
    # when non-groupers are also categorical

    gp = education_df.astype("category").groupby(
        "country", as_index=as_index, observed=observed
    )
    result = gp.value_counts(normalize=normalize)

    expected_index = MultiIndex.from_tuples(
        [
            ("FR", "male", "low"),
            ("FR", "female", "high"),
            ("FR", "male", "medium"),
            ("FR", "female", "low"),
            ("FR", "female", "medium"),
            ("FR", "male", "high"),
            ("US", "female", "high"),
            ("US", "male", "low"),
            ("US", "female", "low"),
            ("US", "female", "medium"),
            ("US", "male", "high"),
            ("US", "male", "medium"),
        ],
        names=["country", "gender", "education"],
    )

    expected_series = Series(
        data=expected_data,
        index=expected_index,
    )
    for i in range(3):
        expected_series.index = expected_series.index.set_levels(
            CategoricalIndex(expected_series.index.levels[i]), level=i
        )

    if as_index:
        tm.assert_series_equal(result, expected_series)
    else:
        expected = expected_series.reset_index(
            name="proportion" if normalize else "count"
        )
        tm.assert_frame_equal(result, expected)


def assert_categorical_single_grouper(
    education_df, as_index, observed, expected_index, normalize, expected_data
):
    # Test single categorical grouper when non-groupers are also categorical
    education_df = education_df.copy().astype("category")

    # Add non-observed grouping categories
    education_df["country"] = education_df["country"].cat.add_categories(["ASIA"])

    gp = education_df.groupby("country", as_index=as_index, observed=observed)
    result = gp.value_counts(normalize=normalize)

    expected_series = Series(
        data=expected_data,
        index=MultiIndex.from_tuples(
            expected_index,
            names=["country", "gender", "education"],
        ),
    )
    for i in range(3):
        index_level = CategoricalIndex(expected_series.index.levels[i])
        if i == 0:
            index_level = index_level.set_categories(
                education_df["country"].cat.categories
            )
        expected_series.index = expected_series.index.set_levels(index_level, level=i)

    if as_index:
        tm.assert_series_equal(result, expected_series)
    else:
        expected = expected_series.reset_index(
            name="proportion" if normalize else "count"
        )
        tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize("as_index", [True, False])
@pytest.mark.parametrize(
    "normalize, expected_data",
    [
        (False, np.array([2, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0], dtype=np.int64)),
        (
            True,
            np.array([0.5, 0.25, 0.25, 0.0, 0.0, 0.0, 0.5, 0.5, 0.0, 0.0, 0.0, 0.0]),
        ),
    ],
)
def test_categorical_single_grouper_observed_true(
    education_df, as_index, normalize, expected_data
):
    # GH#46357

    expected_index = [
        ("FR", "male", "low"),
        ("FR", "female", "high"),
        ("FR", "male", "medium"),
        ("FR", "female", "low"),
        ("FR", "female", "medium"),
        ("FR", "male", "high"),
        ("US", "female", "high"),
        ("US", "male", "low"),
        ("US", "female", "low"),
        ("US", "female", "medium"),
        ("US", "male", "high"),
        ("US", "male", "medium"),
    ]

    assert_categorical_single_grouper(
        education_df=education_df,
        as_index=as_index,
        observed=True,
        expected_index=expected_index,
        normalize=normalize,
        expected_data=expected_data,
    )


@pytest.mark.parametrize("as_index", [True, False])
@pytest.mark.parametrize(
    "normalize, expected_data",
    [
        (
            False,
            np.array(
                [2, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], dtype=np.int64
            ),
        ),
        (
            True,
            np.array(
                [
                    0.5,
                    0.25,
                    0.25,
                    0.0,
                    0.0,
                    0.0,
                    0.5,
                    0.5,
                    0.0,
                    0.0,
                    0.0,
                    0.0,
                    0.0,
                    0.0,
                    0.0,
                    0.0,
                    0.0,
                    0.0,
                ]
            ),
        ),
    ],
)
def test_categorical_single_grouper_observed_false(
    education_df, as_index, normalize, expected_data
):
    # GH#46357

    expected_index = [
        ("FR", "male", "low"),
        ("FR", "female", "high"),
        ("FR", "male", "medium"),
        ("FR", "female", "low"),
        ("FR", "male", "high"),
        ("FR", "female", "medium"),
        ("US", "female", "high"),
        ("US", "male", "low"),
        ("US", "male", "medium"),
        ("US", "male", "high"),
        ("US", "female", "medium"),
        ("US", "female", "low"),
        ("ASIA", "male", "low"),
        ("ASIA", "male", "high"),
        ("ASIA", "female", "medium"),
        ("ASIA", "female", "low"),
        ("ASIA", "female", "high"),
        ("ASIA", "male", "medium"),
    ]

    assert_categorical_single_grouper(
        education_df=education_df,
        as_index=as_index,
        observed=False,
        expected_index=expected_index,
        normalize=normalize,
        expected_data=expected_data,
    )


@pytest.mark.parametrize("as_index", [True, False])
@pytest.mark.parametrize(
    "observed, expected_index",
    [
        (
            False,
            [
                ("FR", "high", "female"),
                ("FR", "high", "male"),
                ("FR", "low", "male"),
                ("FR", "low", "female"),
                ("FR", "medium", "male"),
                ("FR", "medium", "female"),
                ("US", "high", "female"),
                ("US", "high", "male"),
                ("US", "low", "male"),
                ("US", "low", "female"),
                ("US", "medium", "female"),
                ("US", "medium", "male"),
            ],
        ),
        (
            True,
            [
                ("FR", "high", "female"),
                ("FR", "low", "male"),
                ("FR", "medium", "male"),
                ("US", "high", "female"),
                ("US", "low", "male"),
            ],
        ),
    ],
)
@pytest.mark.parametrize(
    "normalize, expected_data",
    [
        (False, np.array([1, 0, 2, 0, 1, 0, 1, 0, 1, 0, 0, 0], dtype=np.int64)),
        (
            True,
            # NaN values corresponds to non-observed groups
            np.array([1.0, 0.0, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0, 0.0, 0.0]),
        ),
    ],
)
def test_categorical_multiple_groupers(
    education_df, as_index, observed, expected_index, normalize, expected_data
):
    # GH#46357

    # Test multiple categorical groupers when non-groupers are non-categorical
    education_df = education_df.copy()
    education_df["country"] = education_df["country"].astype("category")
    education_df["education"] = education_df["education"].astype("category")

    gp = education_df.groupby(
        ["country", "education"], as_index=as_index, observed=observed
    )
    result = gp.value_counts(normalize=normalize)

    expected_series = Series(
        data=expected_data[expected_data > 0.0] if observed else expected_data,
        index=MultiIndex.from_tuples(
            expected_index,
            names=["country", "education", "gender"],
        ),
    )
    for i in range(2):
        expected_series.index = expected_series.index.set_levels(
            CategoricalIndex(expected_series.index.levels[i]), level=i
        )

    if as_index:
        tm.assert_series_equal(result, expected_series)
    else:
        expected = expected_series.reset_index(
            name="proportion" if normalize else "count"
        )
        tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize("as_index", [False, True])
@pytest.mark.parametrize("observed", [False, True])
@pytest.mark.parametrize(
    "normalize, expected_data",
    [
        (False, np.array([2, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0], dtype=np.int64)),
        (
            True,
            # NaN values corresponds to non-observed groups
            np.array([0.5, 0.25, 0.25, 0.0, 0.0, 0.0, 0.5, 0.5, 0.0, 0.0, 0.0, 0.0]),
        ),
    ],
)
def test_categorical_non_groupers(
    education_df, as_index, observed, normalize, expected_data
):
    # GH#46357 Test non-observed categories are included in the result,
    # regardless of `observed`
    education_df = education_df.copy()
    education_df["gender"] = education_df["gender"].astype("category")
    education_df["education"] = education_df["education"].astype("category")

    gp = education_df.groupby("country", as_index=as_index, observed=observed)
    result = gp.value_counts(normalize=normalize)

    expected_index = [
        ("FR", "male", "low"),
        ("FR", "female", "high"),
        ("FR", "male", "medium"),
        ("FR", "female", "low"),
        ("FR", "female", "medium"),
        ("FR", "male", "high"),
        ("US", "female", "high"),
        ("US", "male", "low"),
        ("US", "female", "low"),
        ("US", "female", "medium"),
        ("US", "male", "high"),
        ("US", "male", "medium"),
    ]
    expected_series = Series(
        data=expected_data,
        index=MultiIndex.from_tuples(
            expected_index,
            names=["country", "gender", "education"],
        ),
    )
    for i in range(1, 3):
        expected_series.index = expected_series.index.set_levels(
            CategoricalIndex(expected_series.index.levels[i]), level=i
        )

    if as_index:
        tm.assert_series_equal(result, expected_series)
    else:
        expected = expected_series.reset_index(
            name="proportion" if normalize else "count"
        )
        tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize(
    "normalize, expected_label, expected_values",
    [
        (False, "count", [1, 1, 1]),
        (True, "proportion", [0.5, 0.5, 1.0]),
    ],
)
def test_mixed_groupings(normalize, expected_label, expected_values):
    # Test multiple groupings
    df = DataFrame({"A": [1, 2, 1], "B": [1, 2, 3]})
    gp = df.groupby([[4, 5, 4], "A", lambda i: 7 if i == 1 else 8], as_index=False)
    result = gp.value_counts(sort=True, normalize=normalize)
    expected = DataFrame(
        {
            "level_0": [4, 4, 5],
            "A": [1, 1, 2],
            "level_2": [8, 8, 7],
            "B": [1, 3, 2],
            expected_label: expected_values,
        }
    )
    tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize(
    "test, columns, expected_names",
    [
        ("repeat", list("abbde"), ["a", None, "d", "b", "b", "e"]),
        ("level", list("abcd") + ["level_1"], ["a", None, "d", "b", "c", "level_1"]),
    ],
)
@pytest.mark.parametrize("as_index", [False, True])
def test_column_label_duplicates(test, columns, expected_names, as_index):
    # GH 44992
    # Test for duplicate input column labels and generated duplicate labels
    df = DataFrame([[1, 3, 5, 7, 9], [2, 4, 6, 8, 10]], columns=columns)
    expected_data = [(1, 0, 7, 3, 5, 9), (2, 1, 8, 4, 6, 10)]
    result = df.groupby(["a", [0, 1], "d"], as_index=as_index).value_counts()
    if as_index:
        expected = Series(
            data=(1, 1),
            index=MultiIndex.from_tuples(
                expected_data,
                names=expected_names,
            ),
        )
        tm.assert_series_equal(result, expected)
    else:
        expected_data = [list(row) + [1] for row in expected_data]
        expected_columns = list(expected_names)
        expected_columns[1] = "level_1"
        expected_columns.append("count")
        expected = DataFrame(expected_data, columns=expected_columns)
        tm.assert_frame_equal(result, expected)


@pytest.mark.parametrize(
    "normalize, expected_label",
    [
        (False, "count"),
        (True, "proportion"),
    ],
)
def test_result_label_duplicates(normalize, expected_label):
    # Test for result column label duplicating an input column label
    gb = DataFrame([[1, 2, 3]], columns=["a", "b", expected_label]).groupby(
        "a", as_index=False
    )
    msg = f"Column label '{expected_label}' is duplicate of result column"
    with pytest.raises(ValueError, match=msg):
        gb.value_counts(normalize=normalize)


def test_ambiguous_grouping():
    # Test that groupby is not confused by groupings length equal to row count
    df = DataFrame({"a": [1, 1]})
    gb = df.groupby([1, 1])
    result = gb.value_counts()
    expected = Series([2], index=MultiIndex.from_tuples([[1, 1]], names=[None, "a"]))
    tm.assert_series_equal(result, expected)


def test_subset_overlaps_gb_key_raises():
    # GH 46383
    df = DataFrame({"c1": ["a", "b", "c"], "c2": ["x", "y", "y"]}, index=[0, 1, 1])
    msg = "Keys {'c1'} in subset cannot be in the groupby column keys."
    with pytest.raises(ValueError, match=msg):
        df.groupby("c1").value_counts(subset=["c1"])


def test_subset_doesnt_exist_in_frame():
    # GH 46383
    df = DataFrame({"c1": ["a", "b", "c"], "c2": ["x", "y", "y"]}, index=[0, 1, 1])
    msg = "Keys {'c3'} in subset do not exist in the DataFrame."
    with pytest.raises(ValueError, match=msg):
        df.groupby("c1").value_counts(subset=["c3"])


def test_subset():
    # GH 46383
    df = DataFrame({"c1": ["a", "b", "c"], "c2": ["x", "y", "y"]}, index=[0, 1, 1])
    result = df.groupby(level=0).value_counts(subset=["c2"])
    expected = Series(
        [1, 2], index=MultiIndex.from_arrays([[0, 1], ["x", "y"]], names=[None, "c2"])
    )
    tm.assert_series_equal(result, expected)


def test_subset_duplicate_columns():
    # GH 46383
    df = DataFrame(
        [["a", "x", "x"], ["b", "y", "y"], ["b", "y", "y"]],
        index=[0, 1, 1],
        columns=["c1", "c2", "c2"],
    )
    result = df.groupby(level=0).value_counts(subset=["c2"])
    expected = Series(
        [1, 2],
        index=MultiIndex.from_arrays(
            [[0, 1], ["x", "y"], ["x", "y"]], names=[None, "c2", "c2"]
        ),
    )
    tm.assert_series_equal(result, expected)