groupby.pyx

# -*- coding: utf-8 -*-

cimport cython
from cython cimport Py_ssize_t

from libc.stdlib cimport malloc, free

import numpy as np
cimport numpy as cnp
from numpy cimport (ndarray,
                    double_t,
                    int8_t, int16_t, int32_t, int64_t, uint8_t, uint16_t,
                    uint32_t, uint64_t, float32_t, float64_t)
cnp.import_array()


from util cimport numeric, get_nat

from algos cimport (swap, TiebreakEnumType, TIEBREAK_AVERAGE, TIEBREAK_MIN,
                    TIEBREAK_MAX, TIEBREAK_FIRST, TIEBREAK_DENSE)
from algos import take_2d_axis1_float64_float64, groupsort_indexer, tiebreakers

cdef int64_t iNaT = get_nat()

cdef double NaN = <double> np.NaN
cdef double nan = NaN


cdef inline float64_t median_linear(float64_t* a, int n) nogil:
    cdef:
        int i, j, na_count = 0
        float64_t result
        float64_t* tmp

    if n == 0:
        return NaN

    # count NAs
    for i in range(n):
        if a[i] != a[i]:
            na_count += 1

    if na_count:
        if na_count == n:
            return NaN

        tmp = <float64_t*> malloc((n - na_count) * sizeof(float64_t))

        j = 0
        for i in range(n):
            if a[i] == a[i]:
                tmp[j] = a[i]
                j += 1

        a = tmp
        n -= na_count

    if n % 2:
        result = kth_smallest_c( a, n / 2, n)
    else:
        result = (kth_smallest_c(a, n / 2, n) +
                  kth_smallest_c(a, n / 2 - 1, n)) / 2

    if na_count:
        free(a)

    return result


# TODO: Is this redundant with algos.kth_smallest?
cdef inline float64_t kth_smallest_c(float64_t* a,
                                     Py_ssize_t k,
                                     Py_ssize_t n) nogil:
    cdef:
        Py_ssize_t i, j, l, m
        double_t x, t

    l = 0
    m = n - 1
    while l < m:
        x = a[k]
        i = l
        j = m

        while 1:
            while a[i] < x: i += 1
            while x < a[j]: j -= 1
            if i <= j:
                swap(&a[i], &a[j])
                i += 1; j -= 1

            if i > j: break

        if j < k: l = i
        if k < i: m = j
    return a[k]


@cython.boundscheck(False)
@cython.wraparound(False)
def group_median_float64(ndarray[float64_t, ndim=2] out,
                         ndarray[int64_t] counts,
                         ndarray[float64_t, ndim=2] values,
                         ndarray[int64_t] labels,
                         Py_ssize_t min_count=-1):
    """
    Only aggregates on axis=0
    """
    cdef:
        Py_ssize_t i, j, N, K, ngroups, size
        ndarray[int64_t] _counts
        ndarray data
        float64_t* ptr

    assert min_count == -1, "'min_count' only used in add and prod"

    ngroups = len(counts)
    N, K = (<object> values).shape

    indexer, _counts = groupsort_indexer(labels, ngroups)
    counts[:] = _counts[1:]

    data = np.empty((K, N), dtype=np.float64)
    ptr = <float64_t*> cnp.PyArray_DATA(data)

    take_2d_axis1_float64_float64(values.T, indexer, out=data)

    with nogil:

        for i in range(K):
            # exclude NA group
            ptr += _counts[0]
            for j in range(ngroups):
                size = _counts[j + 1]
                out[j, i] = median_linear(ptr, size)
                ptr += size


@cython.boundscheck(False)
@cython.wraparound(False)
def group_cumprod_float64(float64_t[:, :] out,
                          float64_t[:, :] values,
                          int64_t[:] labels,
                          bint is_datetimelike,
                          bint skipna=True):
    """
    Only transforms on axis=0
    """
    cdef:
        Py_ssize_t i, j, N, K, size
        float64_t val
        float64_t[:, :] accum
        int64_t lab

    N, K = (<object> values).shape
    accum = np.ones_like(values)

    with nogil:
        for i in range(N):
            lab = labels[i]

            if lab < 0:
                continue
            for j in range(K):
                val = values[i, j]
                if val == val:
                    accum[lab, j] *= val
                    out[i, j] = accum[lab, j]
                else:
                    out[i, j] = NaN
                    if not skipna:
                        accum[lab, j] = NaN
                        break


@cython.boundscheck(False)
@cython.wraparound(False)
def group_cumsum(numeric[:, :] out,
                 numeric[:, :] values,
                 int64_t[:] labels,
                 is_datetimelike,
                 bint skipna=True):
    """
    Only transforms on axis=0
    """
    cdef:
        Py_ssize_t i, j, N, K, size
        numeric val
        numeric[:, :] accum
        int64_t lab

    N, K = (<object> values).shape
    accum = np.zeros_like(values)

    with nogil:
        for i in range(N):
            lab = labels[i]

            if lab < 0:
                continue
            for j in range(K):
                val = values[i, j]

                if numeric == float32_t or numeric == float64_t:
                    if val == val:
                        accum[lab, j] += val
                        out[i, j] = accum[lab, j]
                    else:
                        out[i, j] = NaN
                        if not skipna:
                            accum[lab, j] = NaN
                            break
                else:
                    accum[lab, j] += val
                    out[i, j] = accum[lab, j]


@cython.boundscheck(False)
@cython.wraparound(False)
def group_shift_indexer(ndarray[int64_t] out, ndarray[int64_t] labels,
                        int ngroups, int periods):
    cdef:
        Py_ssize_t N, i, j, ii
        int offset, sign
        int64_t lab, idxer, idxer_slot
        int64_t[:] label_seen = np.zeros(ngroups, dtype=np.int64)
        int64_t[:, :] label_indexer

    N, = (<object> labels).shape

    if periods < 0:
        periods = -periods
        offset = N - 1
        sign = -1
    elif periods > 0:
        offset = 0
        sign = 1

    if periods == 0:
        with nogil:
            for i in range(N):
                out[i] = i
    else:
        # array of each previous indexer seen
        label_indexer = np.zeros((ngroups, periods), dtype=np.int64)
        with nogil:
            for i in range(N):
                # reverse iterator if shifting backwards
                ii = offset + sign * i
                lab = labels[ii]

                # Skip null keys
                if lab == -1:
                    out[ii] = -1
                    continue

                label_seen[lab] += 1

                idxer_slot = label_seen[lab] % periods
                idxer = label_indexer[lab, idxer_slot]

                if label_seen[lab] > periods:
                    out[ii] = idxer
                else:
                    out[ii] = -1

                label_indexer[lab, idxer_slot] = ii


@cython.wraparound(False)
@cython.boundscheck(False)
def group_fillna_indexer(ndarray[int64_t] out, ndarray[int64_t] labels,
                         ndarray[uint8_t] mask, object direction,
                         int64_t limit):
    """Indexes how to fill values forwards or backwards within a group

    Parameters
    ----------
    out : array of int64_t values which this method will write its results to
        Missing values will be written to with a value of -1
    labels : array containing unique label for each group, with its ordering
        matching up to the corresponding record in `values`
    mask : array of int64_t values where a 1 indicates a missing value
    direction : {'ffill', 'bfill'}
        Direction for fill to be applied (forwards or backwards, respectively)
    limit : Consecutive values to fill before stopping, or -1 for no limit

    Notes
    -----
    This method modifies the `out` parameter rather than returning an object
    """
    cdef:
        Py_ssize_t i, N
        ndarray[int64_t] sorted_labels
        int64_t idx, curr_fill_idx=-1, filled_vals=0

    N = len(out)

    # Make sure all arrays are the same size
    assert N == len(labels) == len(mask)

    sorted_labels = np.argsort(labels, kind='mergesort').astype(
        np.int64, copy=False)
    if direction == 'bfill':
        sorted_labels = sorted_labels[::-1]

    with nogil:
        for i in range(N):
            idx = sorted_labels[i]
            if mask[idx] == 1:  # is missing
                # Stop filling once we've hit the limit
                if filled_vals >= limit and limit != -1:
                    curr_fill_idx = -1
                filled_vals += 1
            else:  # reset items when not missing
                filled_vals = 0
                curr_fill_idx = idx

            out[idx] = curr_fill_idx

            # If we move to the next group, reset
            # the fill_idx and counter
            if i == N - 1 or labels[idx] != labels[sorted_labels[i + 1]]:
                curr_fill_idx = -1
                filled_vals = 0


@cython.boundscheck(False)
@cython.wraparound(False)
def group_any_all(ndarray[uint8_t] out,
                  ndarray[int64_t] labels,
                  ndarray[uint8_t] values,
                  ndarray[uint8_t] mask,
                  object val_test,
                  bint skipna):
    """Aggregated boolean values to show truthfulness of group elements

    Parameters
    ----------
    out : array of values which this method will write its results to
    labels : array containing unique label for each group, with its
        ordering matching up to the corresponding record in `values`
    values : array containing the truth value of each element
    mask : array indicating whether a value is na or not
    val_test : str {'any', 'all'}
        String object dictating whether to use any or all truth testing
    skipna : boolean
        Flag to ignore nan values during truth testing

    Notes
    -----
    This method modifies the `out` parameter rather than returning an object.
    The returned values will either be 0 or 1 (False or True, respectively).
    """
    cdef:
        Py_ssize_t i, N=len(labels)
        int64_t lab
        uint8_t flag_val

    if val_test == 'all':
        # Because the 'all' value of an empty iterable in Python is True we can
        # start with an array full of ones and set to zero when a False value
        # is encountered
        flag_val = 0
    elif val_test == 'any':
        # Because the 'any' value of an empty iterable in Python is False we
        # can start with an array full of zeros and set to one only if any
        # value encountered is True
        flag_val = 1
    else:
        raise ValueError("'bool_func' must be either 'any' or 'all'!")

    out.fill(1 - flag_val)

    with nogil:
        for i in range(N):
            lab = labels[i]
            if lab < 0 or (skipna and mask[i]):
                continue

            if values[i] == flag_val:
                out[lab] = flag_val


# generated from template
include "groupby_helper.pxi"