""" Tests for statistical reductions of 2nd moment or higher: var, skew, kurt, ... """ import inspect import numpy as np import pytest import pandas.util._test_decorators as td import pandas as pd from pandas import ( DataFrame, Series, ) import pandas._testing as tm from pandas.core.arrays import ( DatetimeArray, PeriodArray, TimedeltaArray, ) class TestDatetimeLikeStatReductions: @pytest.mark.parametrize("box", [Series, pd.Index, DatetimeArray]) def test_dt64_mean(self, tz_naive_fixture, box): tz = tz_naive_fixture dti = pd.date_range("2001-01-01", periods=11, tz=tz) # shuffle so that we are not just working with monotone-increasing dti = dti.take([4, 1, 3, 10, 9, 7, 8, 5, 0, 2, 6]) dtarr = dti._data obj = box(dtarr) assert obj.mean() == pd.Timestamp("2001-01-06", tz=tz) assert obj.mean(skipna=False) == pd.Timestamp("2001-01-06", tz=tz) # dtarr[-2] will be the first date 2001-01-1 dtarr[-2] = pd.NaT obj = box(dtarr) assert obj.mean() == pd.Timestamp("2001-01-06 07:12:00", tz=tz) assert obj.mean(skipna=False) is pd.NaT @pytest.mark.parametrize("box", [Series, pd.Index, PeriodArray]) @pytest.mark.parametrize("freq", ["S", "H", "D", "W", "B"]) def test_period_mean(self, box, freq): # GH#24757 dti = pd.date_range("2001-01-01", periods=11) # shuffle so that we are not just working with monotone-increasing dti = dti.take([4, 1, 3, 10, 9, 7, 8, 5, 0, 2, 6]) parr = dti._data.to_period(freq) obj = box(parr) with pytest.raises(TypeError, match="ambiguous"): obj.mean() with pytest.raises(TypeError, match="ambiguous"): obj.mean(skipna=True) # parr[-2] will be the first date 2001-01-1 parr[-2] = pd.NaT with pytest.raises(TypeError, match="ambiguous"): obj.mean() with pytest.raises(TypeError, match="ambiguous"): obj.mean(skipna=True) @pytest.mark.parametrize("box", [Series, pd.Index, TimedeltaArray]) def test_td64_mean(self, box): tdi = pd.TimedeltaIndex([0, 3, -2, -7, 1, 2, -1, 3, 5, -2, 4], unit="D") tdarr = tdi._data obj = box(tdarr, copy=False) result = obj.mean() expected = np.array(tdarr).mean() assert result == expected tdarr[0] = pd.NaT assert obj.mean(skipna=False) is pd.NaT result2 = obj.mean(skipna=True) assert result2 == tdi[1:].mean() # exact equality fails by 1 nanosecond assert result2.round("us") == (result * 11.0 / 10).round("us") class TestSeriesStatReductions: # Note: the name TestSeriesStatReductions indicates these tests # were moved from a series-specific test file, _not_ that these tests are # intended long-term to be series-specific def _check_stat_op( self, name, alternate, string_series_, check_objects=False, check_allna=False ): with pd.option_context("use_bottleneck", False): f = getattr(Series, name) # add some NaNs string_series_[5:15] = np.NaN # mean, idxmax, idxmin, min, and max are valid for dates if name not in ["max", "min", "mean", "median", "std"]: ds = Series(pd.date_range("1/1/2001", periods=10)) msg = f"does not support reduction '{name}'" with pytest.raises(TypeError, match=msg): f(ds) # skipna or no assert pd.notna(f(string_series_)) assert pd.isna(f(string_series_, skipna=False)) # check the result is correct nona = string_series_.dropna() tm.assert_almost_equal(f(nona), alternate(nona.values)) tm.assert_almost_equal(f(string_series_), alternate(nona.values)) allna = string_series_ * np.nan if check_allna: assert np.isnan(f(allna)) # dtype=object with None, it works! s = Series([1, 2, 3, None, 5]) f(s) # GH#2888 items = [0] items.extend(range(2**40, 2**40 + 1000)) s = Series(items, dtype="int64") tm.assert_almost_equal(float(f(s)), float(alternate(s.values))) # check date range if check_objects: s = Series(pd.bdate_range("1/1/2000", periods=10)) res = f(s) exp = alternate(s) assert res == exp # check on string data if name not in ["sum", "min", "max"]: with pytest.raises(TypeError, match=None): f(Series(list("abc"))) # Invalid axis. msg = "No axis named 1 for object type Series" with pytest.raises(ValueError, match=msg): f(string_series_, axis=1) if "numeric_only" in inspect.getfullargspec(f).args: # only the index is string; dtype is float f(string_series_, numeric_only=True) def test_sum(self): string_series = tm.makeStringSeries().rename("series") self._check_stat_op("sum", np.sum, string_series, check_allna=False) def test_mean(self): string_series = tm.makeStringSeries().rename("series") self._check_stat_op("mean", np.mean, string_series) def test_median(self): string_series = tm.makeStringSeries().rename("series") self._check_stat_op("median", np.median, string_series) # test with integers, test failure int_ts = Series(np.ones(10, dtype=int), index=range(10)) tm.assert_almost_equal(np.median(int_ts), int_ts.median()) def test_prod(self): string_series = tm.makeStringSeries().rename("series") self._check_stat_op("prod", np.prod, string_series) def test_min(self): string_series = tm.makeStringSeries().rename("series") self._check_stat_op("min", np.min, string_series, check_objects=True) def test_max(self): string_series = tm.makeStringSeries().rename("series") self._check_stat_op("max", np.max, string_series, check_objects=True) def test_var_std(self): string_series = tm.makeStringSeries().rename("series") datetime_series = tm.makeTimeSeries().rename("ts") alt = lambda x: np.std(x, ddof=1) self._check_stat_op("std", alt, string_series) alt = lambda x: np.var(x, ddof=1) self._check_stat_op("var", alt, string_series) result = datetime_series.std(ddof=4) expected = np.std(datetime_series.values, ddof=4) tm.assert_almost_equal(result, expected) result = datetime_series.var(ddof=4) expected = np.var(datetime_series.values, ddof=4) tm.assert_almost_equal(result, expected) # 1 - element series with ddof=1 s = datetime_series.iloc[[0]] result = s.var(ddof=1) assert pd.isna(result) result = s.std(ddof=1) assert pd.isna(result) def test_sem(self): string_series = tm.makeStringSeries().rename("series") datetime_series = tm.makeTimeSeries().rename("ts") alt = lambda x: np.std(x, ddof=1) / np.sqrt(len(x)) self._check_stat_op("sem", alt, string_series) result = datetime_series.sem(ddof=4) expected = np.std(datetime_series.values, ddof=4) / np.sqrt( len(datetime_series.values) ) tm.assert_almost_equal(result, expected) # 1 - element series with ddof=1 s = datetime_series.iloc[[0]] result = s.sem(ddof=1) assert pd.isna(result) @td.skip_if_no_scipy def test_skew(self): from scipy.stats import skew string_series = tm.makeStringSeries().rename("series") alt = lambda x: skew(x, bias=False) self._check_stat_op("skew", alt, string_series) # test corner cases, skew() returns NaN unless there's at least 3 # values min_N = 3 for i in range(1, min_N + 1): s = Series(np.ones(i)) df = DataFrame(np.ones((i, i))) if i < min_N: assert np.isnan(s.skew()) assert np.isnan(df.skew()).all() else: assert 0 == s.skew() assert (df.skew() == 0).all() @td.skip_if_no_scipy def test_kurt(self): from scipy.stats import kurtosis string_series = tm.makeStringSeries().rename("series") alt = lambda x: kurtosis(x, bias=False) self._check_stat_op("kurt", alt, string_series) def test_kurt_corner(self): # test corner cases, kurt() returns NaN unless there's at least 4 # values min_N = 4 for i in range(1, min_N + 1): s = Series(np.ones(i)) df = DataFrame(np.ones((i, i))) if i < min_N: assert np.isnan(s.kurt()) assert np.isnan(df.kurt()).all() else: assert 0 == s.kurt() assert (df.kurt() == 0).all()