test_analytics.py

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

from __future__ import print_function

from datetime import timedelta
from distutils.version import LooseVersion
import sys
import pytest

from string import ascii_lowercase
from numpy import nan
from numpy.random import randn
import numpy as np

from pandas.compat import lrange, product
from pandas import (compat, isnull, notnull, DataFrame, Series,
                    MultiIndex, date_range, Timestamp)
import pandas as pd
import pandas.core.nanops as nanops
import pandas.core.algorithms as algorithms
import pandas.io.formats.printing as printing

import pandas.util.testing as tm
from pandas.tests.frame.common import TestData


class TestDataFrameAnalytics(TestData):

    # ---------------------------------------------------------------------=
    # Correlation and covariance

    def test_corr_pearson(self):
        tm._skip_if_no_scipy()
        self.frame['A'][:5] = nan
        self.frame['B'][5:10] = nan

        self._check_method('pearson')

    def test_corr_kendall(self):
        tm._skip_if_no_scipy()
        self.frame['A'][:5] = nan
        self.frame['B'][5:10] = nan

        self._check_method('kendall')

    def test_corr_spearman(self):
        tm._skip_if_no_scipy()
        self.frame['A'][:5] = nan
        self.frame['B'][5:10] = nan

        self._check_method('spearman')

    def _check_method(self, method='pearson', check_minp=False):
        if not check_minp:
            correls = self.frame.corr(method=method)
            exp = self.frame['A'].corr(self.frame['C'], method=method)
            tm.assert_almost_equal(correls['A']['C'], exp)
        else:
            result = self.frame.corr(min_periods=len(self.frame) - 8)
            expected = self.frame.corr()
            expected.loc['A', 'B'] = expected.loc['B', 'A'] = nan
            tm.assert_frame_equal(result, expected)

    def test_corr_non_numeric(self):
        tm._skip_if_no_scipy()
        self.frame['A'][:5] = nan
        self.frame['B'][5:10] = nan

        # exclude non-numeric types
        result = self.mixed_frame.corr()
        expected = self.mixed_frame.loc[:, ['A', 'B', 'C', 'D']].corr()
        tm.assert_frame_equal(result, expected)

    def test_corr_nooverlap(self):
        tm._skip_if_no_scipy()

        # nothing in common
        for meth in ['pearson', 'kendall', 'spearman']:
            df = DataFrame({'A': [1, 1.5, 1, np.nan, np.nan, np.nan],
                            'B': [np.nan, np.nan, np.nan, 1, 1.5, 1],
                            'C': [np.nan, np.nan, np.nan, np.nan,
                                  np.nan, np.nan]})
            rs = df.corr(meth)
            assert isnull(rs.loc['A', 'B'])
            assert isnull(rs.loc['B', 'A'])
            assert rs.loc['A', 'A'] == 1
            assert rs.loc['B', 'B'] == 1
            assert isnull(rs.loc['C', 'C'])

    def test_corr_constant(self):
        tm._skip_if_no_scipy()

        # constant --> all NA

        for meth in ['pearson', 'spearman']:
            df = DataFrame({'A': [1, 1, 1, np.nan, np.nan, np.nan],
                            'B': [np.nan, np.nan, np.nan, 1, 1, 1]})
            rs = df.corr(meth)
            assert isnull(rs.values).all()

    def test_corr_int(self):
        # dtypes other than float64 #1761
        df3 = DataFrame({"a": [1, 2, 3, 4], "b": [1, 2, 3, 4]})

        # it works!
        df3.cov()
        df3.corr()

    def test_corr_int_and_boolean(self):
        tm._skip_if_no_scipy()

        # when dtypes of pandas series are different
        # then ndarray will have dtype=object,
        # so it need to be properly handled
        df = DataFrame({"a": [True, False], "b": [1, 0]})

        expected = DataFrame(np.ones((2, 2)), index=[
                             'a', 'b'], columns=['a', 'b'])
        for meth in ['pearson', 'kendall', 'spearman']:
            tm.assert_frame_equal(df.corr(meth), expected)

    def test_corr_cov_independent_index_column(self):
        # GH 14617
        df = pd.DataFrame(np.random.randn(4 * 10).reshape(10, 4),
                          columns=list("abcd"))
        for method in ['cov', 'corr']:
            result = getattr(df, method)()
            assert result.index is not result.columns
            assert result.index.equals(result.columns)

    def test_cov(self):
        # min_periods no NAs (corner case)
        expected = self.frame.cov()
        result = self.frame.cov(min_periods=len(self.frame))

        tm.assert_frame_equal(expected, result)

        result = self.frame.cov(min_periods=len(self.frame) + 1)
        assert isnull(result.values).all()

        # with NAs
        frame = self.frame.copy()
        frame['A'][:5] = nan
        frame['B'][5:10] = nan
        result = self.frame.cov(min_periods=len(self.frame) - 8)
        expected = self.frame.cov()
        expected.loc['A', 'B'] = np.nan
        expected.loc['B', 'A'] = np.nan

        # regular
        self.frame['A'][:5] = nan
        self.frame['B'][:10] = nan
        cov = self.frame.cov()

        tm.assert_almost_equal(cov['A']['C'],
                               self.frame['A'].cov(self.frame['C']))

        # exclude non-numeric types
        result = self.mixed_frame.cov()
        expected = self.mixed_frame.loc[:, ['A', 'B', 'C', 'D']].cov()
        tm.assert_frame_equal(result, expected)

        # Single column frame
        df = DataFrame(np.linspace(0.0, 1.0, 10))
        result = df.cov()
        expected = DataFrame(np.cov(df.values.T).reshape((1, 1)),
                             index=df.columns, columns=df.columns)
        tm.assert_frame_equal(result, expected)
        df.loc[0] = np.nan
        result = df.cov()
        expected = DataFrame(np.cov(df.values[1:].T).reshape((1, 1)),
                             index=df.columns, columns=df.columns)
        tm.assert_frame_equal(result, expected)

    def test_corrwith(self):
        a = self.tsframe
        noise = Series(randn(len(a)), index=a.index)

        b = self.tsframe.add(noise, axis=0)

        # make sure order does not matter
        b = b.reindex(columns=b.columns[::-1], index=b.index[::-1][10:])
        del b['B']

        colcorr = a.corrwith(b, axis=0)
        tm.assert_almost_equal(colcorr['A'], a['A'].corr(b['A']))

        rowcorr = a.corrwith(b, axis=1)
        tm.assert_series_equal(rowcorr, a.T.corrwith(b.T, axis=0))

        dropped = a.corrwith(b, axis=0, drop=True)
        tm.assert_almost_equal(dropped['A'], a['A'].corr(b['A']))
        assert 'B' not in dropped

        dropped = a.corrwith(b, axis=1, drop=True)
        assert a.index[-1] not in dropped.index

        # non time-series data
        index = ['a', 'b', 'c', 'd', 'e']
        columns = ['one', 'two', 'three', 'four']
        df1 = DataFrame(randn(5, 4), index=index, columns=columns)
        df2 = DataFrame(randn(4, 4), index=index[:4], columns=columns)
        correls = df1.corrwith(df2, axis=1)
        for row in index[:4]:
            tm.assert_almost_equal(correls[row],
                                   df1.loc[row].corr(df2.loc[row]))

    def test_corrwith_with_objects(self):
        df1 = tm.makeTimeDataFrame()
        df2 = tm.makeTimeDataFrame()
        cols = ['A', 'B', 'C', 'D']

        df1['obj'] = 'foo'
        df2['obj'] = 'bar'

        result = df1.corrwith(df2)
        expected = df1.loc[:, cols].corrwith(df2.loc[:, cols])
        tm.assert_series_equal(result, expected)

        result = df1.corrwith(df2, axis=1)
        expected = df1.loc[:, cols].corrwith(df2.loc[:, cols], axis=1)
        tm.assert_series_equal(result, expected)

    def test_corrwith_series(self):
        result = self.tsframe.corrwith(self.tsframe['A'])
        expected = self.tsframe.apply(self.tsframe['A'].corr)

        tm.assert_series_equal(result, expected)

    def test_corrwith_matches_corrcoef(self):
        df1 = DataFrame(np.arange(10000), columns=['a'])
        df2 = DataFrame(np.arange(10000) ** 2, columns=['a'])
        c1 = df1.corrwith(df2)['a']
        c2 = np.corrcoef(df1['a'], df2['a'])[0][1]

        tm.assert_almost_equal(c1, c2)
        assert c1 < 1

    def test_bool_describe_in_mixed_frame(self):
        df = DataFrame({
            'string_data': ['a', 'b', 'c', 'd', 'e'],
            'bool_data': [True, True, False, False, False],
            'int_data': [10, 20, 30, 40, 50],
        })

        # Integer data are included in .describe() output,
        # Boolean and string data are not.
        result = df.describe()
        expected = DataFrame({'int_data': [5, 30, df.int_data.std(),
                                           10, 20, 30, 40, 50]},
                             index=['count', 'mean', 'std', 'min', '25%',
                                    '50%', '75%', 'max'])
        tm.assert_frame_equal(result, expected)

        # Top value is a boolean value that is False
        result = df.describe(include=['bool'])

        expected = DataFrame({'bool_data': [5, 2, False, 3]},
                             index=['count', 'unique', 'top', 'freq'])
        tm.assert_frame_equal(result, expected)

    def test_describe_bool_frame(self):
        # GH 13891
        df = pd.DataFrame({
            'bool_data_1': [False, False, True, True],
            'bool_data_2': [False, True, True, True]
        })
        result = df.describe()
        expected = DataFrame({'bool_data_1': [4, 2, True, 2],
                              'bool_data_2': [4, 2, True, 3]},
                             index=['count', 'unique', 'top', 'freq'])
        tm.assert_frame_equal(result, expected)

        df = pd.DataFrame({
            'bool_data': [False, False, True, True, False],
            'int_data': [0, 1, 2, 3, 4]
        })
        result = df.describe()
        expected = DataFrame({'int_data': [5, 2, df.int_data.std(), 0, 1,
                                           2, 3, 4]},
                             index=['count', 'mean', 'std', 'min', '25%',
                                    '50%', '75%', 'max'])
        tm.assert_frame_equal(result, expected)

        df = pd.DataFrame({
            'bool_data': [False, False, True, True],
            'str_data': ['a', 'b', 'c', 'a']
        })
        result = df.describe()
        expected = DataFrame({'bool_data': [4, 2, True, 2],
                              'str_data': [4, 3, 'a', 2]},
                             index=['count', 'unique', 'top', 'freq'])
        tm.assert_frame_equal(result, expected)

    def test_describe_categorical_columns(self):
        # GH 11558
        columns = pd.CategoricalIndex(['int1', 'int2', 'obj'],
                                      ordered=True, name='XXX')
        df = DataFrame({'int1': [10, 20, 30, 40, 50],
                        'int2': [10, 20, 30, 40, 50],
                        'obj': ['A', 0, None, 'X', 1]},
                       columns=columns)
        result = df.describe()

        exp_columns = pd.CategoricalIndex(['int1', 'int2'],
                                          categories=['int1', 'int2', 'obj'],
                                          ordered=True, name='XXX')
        expected = DataFrame({'int1': [5, 30, df.int1.std(),
                                       10, 20, 30, 40, 50],
                              'int2': [5, 30, df.int2.std(),
                                       10, 20, 30, 40, 50]},
                             index=['count', 'mean', 'std', 'min', '25%',
                                    '50%', '75%', 'max'],
                             columns=exp_columns)
        tm.assert_frame_equal(result, expected)
        tm.assert_categorical_equal(result.columns.values,
                                    expected.columns.values)

    def test_describe_datetime_columns(self):
        columns = pd.DatetimeIndex(['2011-01-01', '2011-02-01', '2011-03-01'],
                                   freq='MS', tz='US/Eastern', name='XXX')
        df = DataFrame({0: [10, 20, 30, 40, 50],
                        1: [10, 20, 30, 40, 50],
                        2: ['A', 0, None, 'X', 1]})
        df.columns = columns
        result = df.describe()

        exp_columns = pd.DatetimeIndex(['2011-01-01', '2011-02-01'],
                                       freq='MS', tz='US/Eastern', name='XXX')
        expected = DataFrame({0: [5, 30, df.iloc[:, 0].std(),
                                  10, 20, 30, 40, 50],
                              1: [5, 30, df.iloc[:, 1].std(),
                                  10, 20, 30, 40, 50]},
                             index=['count', 'mean', 'std', 'min', '25%',
                                    '50%', '75%', 'max'])
        expected.columns = exp_columns
        tm.assert_frame_equal(result, expected)
        assert result.columns.freq == 'MS'
        assert result.columns.tz == expected.columns.tz

    def test_describe_timedelta_values(self):
        # GH 6145
        t1 = pd.timedelta_range('1 days', freq='D', periods=5)
        t2 = pd.timedelta_range('1 hours', freq='H', periods=5)
        df = pd.DataFrame({'t1': t1, 't2': t2})

        expected = DataFrame({'t1': [5, pd.Timedelta('3 days'),
                                     df.iloc[:, 0].std(),
                                     pd.Timedelta('1 days'),
                                     pd.Timedelta('2 days'),
                                     pd.Timedelta('3 days'),
                                     pd.Timedelta('4 days'),
                                     pd.Timedelta('5 days')],
                              't2': [5, pd.Timedelta('3 hours'),
                                     df.iloc[:, 1].std(),
                                     pd.Timedelta('1 hours'),
                                     pd.Timedelta('2 hours'),
                                     pd.Timedelta('3 hours'),
                                     pd.Timedelta('4 hours'),
                                     pd.Timedelta('5 hours')]},
                             index=['count', 'mean', 'std', 'min', '25%',
                                    '50%', '75%', 'max'])

        res = df.describe()
        tm.assert_frame_equal(res, expected)

        exp_repr = ("                           t1                      t2\n"
                    "count                       5                       5\n"
                    "mean          3 days 00:00:00         0 days 03:00:00\n"
                    "std    1 days 13:56:50.394919  0 days 01:34:52.099788\n"
                    "min           1 days 00:00:00         0 days 01:00:00\n"
                    "25%           2 days 00:00:00         0 days 02:00:00\n"
                    "50%           3 days 00:00:00         0 days 03:00:00\n"
                    "75%           4 days 00:00:00         0 days 04:00:00\n"
                    "max           5 days 00:00:00         0 days 05:00:00")
        assert repr(res) == exp_repr

    def test_reduce_mixed_frame(self):
        # GH 6806
        df = DataFrame({
            'bool_data': [True, True, False, False, False],
            'int_data': [10, 20, 30, 40, 50],
            'string_data': ['a', 'b', 'c', 'd', 'e'],
        })
        df.reindex(columns=['bool_data', 'int_data', 'string_data'])
        test = df.sum(axis=0)
        tm.assert_numpy_array_equal(test.values,
                                    np.array([2, 150, 'abcde'], dtype=object))
        tm.assert_series_equal(test, df.T.sum(axis=1))

    def test_count(self):
        f = lambda s: notnull(s).sum()
        self._check_stat_op('count', f,
                            has_skipna=False,
                            has_numeric_only=True,
                            check_dtype=False,
                            check_dates=True)

        # corner case
        frame = DataFrame()
        ct1 = frame.count(1)
        assert isinstance(ct1, Series)

        ct2 = frame.count(0)
        assert isinstance(ct2, Series)

        # GH #423
        df = DataFrame(index=lrange(10))
        result = df.count(1)
        expected = Series(0, index=df.index)
        tm.assert_series_equal(result, expected)

        df = DataFrame(columns=lrange(10))
        result = df.count(0)
        expected = Series(0, index=df.columns)
        tm.assert_series_equal(result, expected)

        df = DataFrame()
        result = df.count()
        expected = Series(0, index=[])
        tm.assert_series_equal(result, expected)

    def test_nunique(self):
        f = lambda s: len(algorithms.unique1d(s.dropna()))
        self._check_stat_op('nunique', f, has_skipna=False,
                            check_dtype=False, check_dates=True)

        df = DataFrame({'A': [1, 1, 1],
                        'B': [1, 2, 3],
                        'C': [1, np.nan, 3]})
        tm.assert_series_equal(df.nunique(), Series({'A': 1, 'B': 3, 'C': 2}))
        tm.assert_series_equal(df.nunique(dropna=False),
                               Series({'A': 1, 'B': 3, 'C': 3}))
        tm.assert_series_equal(df.nunique(axis=1), Series({0: 1, 1: 2, 2: 2}))
        tm.assert_series_equal(df.nunique(axis=1, dropna=False),
                               Series({0: 1, 1: 3, 2: 2}))

    def test_sum(self):
        self._check_stat_op('sum', np.sum, has_numeric_only=True)

        # mixed types (with upcasting happening)
        self._check_stat_op('sum', np.sum,
                            frame=self.mixed_float.astype('float32'),
                            has_numeric_only=True, check_dtype=False,
                            check_less_precise=True)

    def test_stat_operators_attempt_obj_array(self):
        data = {
            'a': [-0.00049987540199591344, -0.0016467257772919831,
                  0.00067695870775883013],
            'b': [-0, -0, 0.0],
            'c': [0.00031111847529610595, 0.0014902627951905339,
                  -0.00094099200035979691]
        }
        df1 = DataFrame(data, index=['foo', 'bar', 'baz'],
                        dtype='O')
        methods = ['sum', 'mean', 'prod', 'var', 'std', 'skew', 'min', 'max']

        # GH #676
        df2 = DataFrame({0: [np.nan, 2], 1: [np.nan, 3],
                         2: [np.nan, 4]}, dtype=object)

        for df in [df1, df2]:
            for meth in methods:
                assert df.values.dtype == np.object_
                result = getattr(df, meth)(1)
                expected = getattr(df.astype('f8'), meth)(1)

                if not tm._incompat_bottleneck_version(meth):
                    tm.assert_series_equal(result, expected)

    def test_mean(self):
        self._check_stat_op('mean', np.mean, check_dates=True)

    def test_product(self):
        self._check_stat_op('product', np.prod)

    def test_median(self):
        def wrapper(x):
            if isnull(x).any():
                return np.nan
            return np.median(x)

        self._check_stat_op('median', wrapper, check_dates=True)

    def test_min(self):
        self._check_stat_op('min', np.min, check_dates=True)
        self._check_stat_op('min', np.min, frame=self.intframe)

    def test_cummin(self):
        self.tsframe.loc[5:10, 0] = nan
        self.tsframe.loc[10:15, 1] = nan
        self.tsframe.loc[15:, 2] = nan

        # axis = 0
        cummin = self.tsframe.cummin()
        expected = self.tsframe.apply(Series.cummin)
        tm.assert_frame_equal(cummin, expected)

        # axis = 1
        cummin = self.tsframe.cummin(axis=1)
        expected = self.tsframe.apply(Series.cummin, axis=1)
        tm.assert_frame_equal(cummin, expected)

        # it works
        df = DataFrame({'A': np.arange(20)}, index=np.arange(20))
        result = df.cummin()  # noqa

        # fix issue
        cummin_xs = self.tsframe.cummin(axis=1)
        assert np.shape(cummin_xs) == np.shape(self.tsframe)

    def test_cummax(self):
        self.tsframe.loc[5:10, 0] = nan
        self.tsframe.loc[10:15, 1] = nan
        self.tsframe.loc[15:, 2] = nan

        # axis = 0
        cummax = self.tsframe.cummax()
        expected = self.tsframe.apply(Series.cummax)
        tm.assert_frame_equal(cummax, expected)

        # axis = 1
        cummax = self.tsframe.cummax(axis=1)
        expected = self.tsframe.apply(Series.cummax, axis=1)
        tm.assert_frame_equal(cummax, expected)

        # it works
        df = DataFrame({'A': np.arange(20)}, index=np.arange(20))
        result = df.cummax()  # noqa

        # fix issue
        cummax_xs = self.tsframe.cummax(axis=1)
        assert np.shape(cummax_xs) == np.shape(self.tsframe)

    def test_max(self):
        self._check_stat_op('max', np.max, check_dates=True)
        self._check_stat_op('max', np.max, frame=self.intframe)

    def test_mad(self):
        f = lambda x: np.abs(x - x.mean()).mean()
        self._check_stat_op('mad', f)

    def test_var_std(self):
        alt = lambda x: np.var(x, ddof=1)
        self._check_stat_op('var', alt)

        alt = lambda x: np.std(x, ddof=1)
        self._check_stat_op('std', alt)

        result = self.tsframe.std(ddof=4)
        expected = self.tsframe.apply(lambda x: x.std(ddof=4))
        tm.assert_almost_equal(result, expected)

        result = self.tsframe.var(ddof=4)
        expected = self.tsframe.apply(lambda x: x.var(ddof=4))
        tm.assert_almost_equal(result, expected)

        arr = np.repeat(np.random.random((1, 1000)), 1000, 0)
        result = nanops.nanvar(arr, axis=0)
        assert not (result < 0).any()
        if nanops._USE_BOTTLENECK:
            nanops._USE_BOTTLENECK = False
            result = nanops.nanvar(arr, axis=0)
            assert not (result < 0).any()
            nanops._USE_BOTTLENECK = True

    def test_numeric_only_flag(self):
        # GH #9201
        methods = ['sem', 'var', 'std']
        df1 = DataFrame(np.random.randn(5, 3), columns=['foo', 'bar', 'baz'])
        # set one entry to a number in str format
        df1.loc[0, 'foo'] = '100'

        df2 = DataFrame(np.random.randn(5, 3), columns=['foo', 'bar', 'baz'])
        # set one entry to a non-number str
        df2.loc[0, 'foo'] = 'a'

        for meth in methods:
            result = getattr(df1, meth)(axis=1, numeric_only=True)
            expected = getattr(df1[['bar', 'baz']], meth)(axis=1)
            tm.assert_series_equal(expected, result)

            result = getattr(df2, meth)(axis=1, numeric_only=True)
            expected = getattr(df2[['bar', 'baz']], meth)(axis=1)
            tm.assert_series_equal(expected, result)

            # df1 has all numbers, df2 has a letter inside
            pytest.raises(TypeError, lambda: getattr(df1, meth)(
                axis=1, numeric_only=False))
            pytest.raises(TypeError, lambda: getattr(df2, meth)(
                axis=1, numeric_only=False))

    def test_mixed_ops(self):
        # GH 16116
        df = DataFrame({'int': [1, 2, 3, 4],
                        'float': [1., 2., 3., 4.],
                        'str': ['a', 'b', 'c', 'd']})

        for op in ['mean', 'std', 'var', 'skew',
                   'kurt', 'sem']:
            result = getattr(df, op)()
            assert len(result) == 2

            if nanops._USE_BOTTLENECK:
                nanops._USE_BOTTLENECK = False
                result = getattr(df, op)()
                assert len(result) == 2
                nanops._USE_BOTTLENECK = True

    def test_cumsum(self):
        self.tsframe.loc[5:10, 0] = nan
        self.tsframe.loc[10:15, 1] = nan
        self.tsframe.loc[15:, 2] = nan

        # axis = 0
        cumsum = self.tsframe.cumsum()
        expected = self.tsframe.apply(Series.cumsum)
        tm.assert_frame_equal(cumsum, expected)

        # axis = 1
        cumsum = self.tsframe.cumsum(axis=1)
        expected = self.tsframe.apply(Series.cumsum, axis=1)
        tm.assert_frame_equal(cumsum, expected)

        # works
        df = DataFrame({'A': np.arange(20)}, index=np.arange(20))
        result = df.cumsum()  # noqa

        # fix issue
        cumsum_xs = self.tsframe.cumsum(axis=1)
        assert np.shape(cumsum_xs) == np.shape(self.tsframe)

    def test_cumprod(self):
        self.tsframe.loc[5:10, 0] = nan
        self.tsframe.loc[10:15, 1] = nan
        self.tsframe.loc[15:, 2] = nan

        # axis = 0
        cumprod = self.tsframe.cumprod()
        expected = self.tsframe.apply(Series.cumprod)
        tm.assert_frame_equal(cumprod, expected)

        # axis = 1
        cumprod = self.tsframe.cumprod(axis=1)
        expected = self.tsframe.apply(Series.cumprod, axis=1)
        tm.assert_frame_equal(cumprod, expected)

        # fix issue
        cumprod_xs = self.tsframe.cumprod(axis=1)
        assert np.shape(cumprod_xs) == np.shape(self.tsframe)

        # ints
        df = self.tsframe.fillna(0).astype(int)
        df.cumprod(0)
        df.cumprod(1)

        # ints32
        df = self.tsframe.fillna(0).astype(np.int32)
        df.cumprod(0)
        df.cumprod(1)

    def test_sem(self):
        alt = lambda x: np.std(x, ddof=1) / np.sqrt(len(x))
        self._check_stat_op('sem', alt)

        result = self.tsframe.sem(ddof=4)
        expected = self.tsframe.apply(
            lambda x: x.std(ddof=4) / np.sqrt(len(x)))
        tm.assert_almost_equal(result, expected)

        arr = np.repeat(np.random.random((1, 1000)), 1000, 0)
        result = nanops.nansem(arr, axis=0)
        assert not (result < 0).any()
        if nanops._USE_BOTTLENECK:
            nanops._USE_BOTTLENECK = False
            result = nanops.nansem(arr, axis=0)
            assert not (result < 0).any()
            nanops._USE_BOTTLENECK = True

    def test_skew(self):
        tm._skip_if_no_scipy()
        from scipy.stats import skew

        def alt(x):
            if len(x) < 3:
                return np.nan
            return skew(x, bias=False)

        self._check_stat_op('skew', alt)

    def test_kurt(self):
        tm._skip_if_no_scipy()

        from scipy.stats import kurtosis

        def alt(x):
            if len(x) < 4:
                return np.nan
            return kurtosis(x, bias=False)

        self._check_stat_op('kurt', alt)

        index = MultiIndex(levels=[['bar'], ['one', 'two', 'three'], [0, 1]],
                           labels=[[0, 0, 0, 0, 0, 0],
                                   [0, 1, 2, 0, 1, 2],
                                   [0, 1, 0, 1, 0, 1]])
        df = DataFrame(np.random.randn(6, 3), index=index)

        kurt = df.kurt()
        kurt2 = df.kurt(level=0).xs('bar')
        tm.assert_series_equal(kurt, kurt2, check_names=False)
        assert kurt.name is None
        assert kurt2.name == 'bar'

    def _check_stat_op(self, name, alternative, frame=None, has_skipna=True,
                       has_numeric_only=False, check_dtype=True,
                       check_dates=False, check_less_precise=False):
        if frame is None:
            frame = self.frame
            # set some NAs
            frame.loc[5:10] = np.nan
            frame.loc[15:20, -2:] = np.nan

        f = getattr(frame, name)

        if check_dates:
            df = DataFrame({'b': date_range('1/1/2001', periods=2)})
            _f = getattr(df, name)
            result = _f()
            assert isinstance(result, Series)

            df['a'] = lrange(len(df))
            result = getattr(df, name)()
            assert isinstance(result, Series)
            assert len(result)

        if has_skipna:
            def skipna_wrapper(x):
                nona = x.dropna()
                if len(nona) == 0:
                    return np.nan
                return alternative(nona)

            def wrapper(x):
                return alternative(x.values)

            result0 = f(axis=0, skipna=False)
            result1 = f(axis=1, skipna=False)
            tm.assert_series_equal(result0, frame.apply(wrapper),
                                   check_dtype=check_dtype,
                                   check_less_precise=check_less_precise)
            # HACK: win32
            tm.assert_series_equal(result1, frame.apply(wrapper, axis=1),
                                   check_dtype=False,
                                   check_less_precise=check_less_precise)
        else:
            skipna_wrapper = alternative
            wrapper = alternative

        result0 = f(axis=0)
        result1 = f(axis=1)
        tm.assert_series_equal(result0, frame.apply(skipna_wrapper),
                               check_dtype=check_dtype,
                               check_less_precise=check_less_precise)
        if not tm._incompat_bottleneck_version(name):
            exp = frame.apply(skipna_wrapper, axis=1)
            tm.assert_series_equal(result1, exp, check_dtype=False,
                                   check_less_precise=check_less_precise)

        # check dtypes
        if check_dtype:
            lcd_dtype = frame.values.dtype
            assert lcd_dtype == result0.dtype
            assert lcd_dtype == result1.dtype

        # result = f(axis=1)
        # comp = frame.apply(alternative, axis=1).reindex(result.index)
        # assert_series_equal(result, comp)

        # bad axis
        tm.assert_raises_regex(ValueError, 'No axis named 2', f, axis=2)
        # make sure works on mixed-type frame
        getattr(self.mixed_frame, name)(axis=0)
        getattr(self.mixed_frame, name)(axis=1)

        if has_numeric_only:
            getattr(self.mixed_frame, name)(axis=0, numeric_only=True)
            getattr(self.mixed_frame, name)(axis=1, numeric_only=True)
            getattr(self.frame, name)(axis=0, numeric_only=False)
            getattr(self.frame, name)(axis=1, numeric_only=False)

        # all NA case
        if has_skipna:
            all_na = self.frame * np.NaN
            r0 = getattr(all_na, name)(axis=0)
            r1 = getattr(all_na, name)(axis=1)
            if not tm._incompat_bottleneck_version(name):
                assert np.isnan(r0).all()
                assert np.isnan(r1).all()

    def test_mode(self):
        df = pd.DataFrame({"A": [12, 12, 11, 12, 19, 11],
                           "B": [10, 10, 10, np.nan, 3, 4],
                           "C": [8, 8, 8, 9, 9, 9],
                           "D": np.arange(6, dtype='int64'),
                           "E": [8, 8, 1, 1, 3, 3]})
        tm.assert_frame_equal(df[["A"]].mode(),
                              pd.DataFrame({"A": [12]}))
        expected = pd.Series([0, 1, 2, 3, 4, 5], dtype='int64', name='D').\
            to_frame()
        tm.assert_frame_equal(df[["D"]].mode(), expected)
        expected = pd.Series([1, 3, 8], dtype='int64', name='E').to_frame()
        tm.assert_frame_equal(df[["E"]].mode(), expected)
        tm.assert_frame_equal(df[["A", "B"]].mode(),
                              pd.DataFrame({"A": [12], "B": [10.]}))
        tm.assert_frame_equal(df.mode(),
                              pd.DataFrame({"A": [12, np.nan, np.nan, np.nan,
                                                  np.nan, np.nan],
                                            "B": [10, np.nan, np.nan, np.nan,
                                                  np.nan, np.nan],
                                            "C": [8, 9, np.nan, np.nan, np.nan,
                                                  np.nan],
                                            "D": [0, 1, 2, 3, 4, 5],
                                            "E": [1, 3, 8, np.nan, np.nan,
                                                  np.nan]}))

        # outputs in sorted order
        df["C"] = list(reversed(df["C"]))
        printing.pprint_thing(df["C"])
        printing.pprint_thing(df["C"].mode())
        a, b = (df[["A", "B", "C"]].mode(),
                pd.DataFrame({"A": [12, np.nan],
                              "B": [10, np.nan],
                              "C": [8, 9]}))
        printing.pprint_thing(a)
        printing.pprint_thing(b)
        tm.assert_frame_equal(a, b)
        # should work with heterogeneous types
        df = pd.DataFrame({"A": np.arange(6, dtype='int64'),
                           "B": pd.date_range('2011', periods=6),
                           "C": list('abcdef')})
        exp = pd.DataFrame({"A": pd.Series(np.arange(6, dtype='int64'),
                                           dtype=df["A"].dtype),
                            "B": pd.Series(pd.date_range('2011', periods=6),
                                           dtype=df["B"].dtype),
                            "C": pd.Series(list('abcdef'),
                                           dtype=df["C"].dtype)})
        tm.assert_frame_equal(df.mode(), exp)

    def test_operators_timedelta64(self):
        from datetime import timedelta
        df = DataFrame(dict(A=date_range('2012-1-1', periods=3, freq='D'),
                            B=date_range('2012-1-2', periods=3, freq='D'),
                            C=Timestamp('20120101') -
                            timedelta(minutes=5, seconds=5)))

        diffs = DataFrame(dict(A=df['A'] - df['C'],
                               B=df['A'] - df['B']))

        # min
        result = diffs.min()
        assert result[0] == diffs.loc[0, 'A']
        assert result[1] == diffs.loc[0, 'B']

        result = diffs.min(axis=1)
        assert (result == diffs.loc[0, 'B']).all()

        # max
        result = diffs.max()
        assert result[0] == diffs.loc[2, 'A']
        assert result[1] == diffs.loc[2, 'B']

        result = diffs.max(axis=1)
        assert (result == diffs['A']).all()

        # abs
        result = diffs.abs()
        result2 = abs(diffs)
        expected = DataFrame(dict(A=df['A'] - df['C'],
                                  B=df['B'] - df['A']))
        tm.assert_frame_equal(result, expected)
        tm.assert_frame_equal(result2, expected)

        # mixed frame
        mixed = diffs.copy()
        mixed['C'] = 'foo'
        mixed['D'] = 1
        mixed['E'] = 1.
        mixed['F'] = Timestamp('20130101')

        # results in an object array
        from pandas.core.tools.timedeltas import (
            _coerce_scalar_to_timedelta_type as _coerce)

        result = mixed.min()
        expected = Series([_coerce(timedelta(seconds=5 * 60 + 5)),
                           _coerce(timedelta(days=-1)),
                           'foo', 1, 1.0,
                           Timestamp('20130101')],
                          index=mixed.columns)
        tm.assert_series_equal(result, expected)

        # excludes numeric
        result = mixed.min(axis=1)
        expected = Series([1, 1, 1.], index=[0, 1, 2])
        tm.assert_series_equal(result, expected)

        # works when only those columns are selected
        result = mixed[['A', 'B']].min(1)
        expected = Series([timedelta(days=-1)] * 3)
        tm.assert_series_equal(result, expected)

        result = mixed[['A', 'B']].min()
        expected = Series([timedelta(seconds=5 * 60 + 5),
                           timedelta(days=-1)], index=['A', 'B'])
        tm.assert_series_equal(result, expected)

        # GH 3106
        df = DataFrame({'time': date_range('20130102', periods=5),
                        'time2': date_range('20130105', periods=5)})
        df['off1'] = df['time2'] - df['time']
        assert df['off1'].dtype == 'timedelta64[ns]'

        df['off2'] = df['time'] - df['time2']
        df._consolidate_inplace()
        assert df['off1'].dtype == 'timedelta64[ns]'
        assert df['off2'].dtype == 'timedelta64[ns]'

    def test_sum_corner(self):
        axis0 = self.empty.sum(0)
        axis1 = self.empty.sum(1)
        assert isinstance(axis0, Series)
        assert isinstance(axis1, Series)
        assert len(axis0) == 0
        assert len(axis1) == 0

    def test_sum_object(self):
        values = self.frame.values.astype(int)
        frame = DataFrame(values, index=self.frame.index,
                          columns=self.frame.columns)
        deltas = frame * timedelta(1)
        deltas.sum()

    def test_sum_bool(self):
        # ensure this works, bug report
        bools = np.isnan(self.frame)
        bools.sum(1)
        bools.sum(0)

    def test_mean_corner(self):
        # unit test when have object data
        the_mean = self.mixed_frame.mean(axis=0)
        the_sum = self.mixed_frame.sum(axis=0, numeric_only=True)
        tm.assert_index_equal(the_sum.index, the_mean.index)
        assert len(the_mean.index) < len(self.mixed_frame.columns)

        # xs sum mixed type, just want to know it works...
        the_mean = self.mixed_frame.mean(axis=1)
        the_sum = self.mixed_frame.sum(axis=1, numeric_only=True)
        tm.assert_index_equal(the_sum.index, the_mean.index)

        # take mean of boolean column
        self.frame['bool'] = self.frame['A'] > 0
        means = self.frame.mean(0)
        assert means['bool'] == self.frame['bool'].values.mean()

    def test_stats_mixed_type(self):
        # don't blow up
        self.mixed_frame.std(1)
        self.mixed_frame.var(1)
        self.mixed_frame.mean(1)
        self.mixed_frame.skew(1)

    def test_median_corner(self):
        def wrapper(x):
            if isnull(x).any():
                return np.nan
            return np.median(x)

        self._check_stat_op('median', wrapper, frame=self.intframe,
                            check_dtype=False, check_dates=True)

    # Miscellanea

    def test_count_objects(self):
        dm = DataFrame(self.mixed_frame._series)
        df = DataFrame(self.mixed_frame._series)

        tm.assert_series_equal(dm.count(), df.count())
        tm.assert_series_equal(dm.count(1), df.count(1))

    def test_cumsum_corner(self):
        dm = DataFrame(np.arange(20).reshape(4, 5),
                       index=lrange(4), columns=lrange(5))
        # ?(wesm)
        result = dm.cumsum()  # noqa

    def test_sum_bools(self):
        df = DataFrame(index=lrange(1), columns=lrange(10))
        bools = isnull(df)
        assert bools.sum(axis=1)[0] == 10

    # Index of max / min

    def test_idxmin(self):
        frame = self.frame
        frame.loc[5:10] = np.nan
        frame.loc[15:20, -2:] = np.nan
        for skipna in [True, False]:
            for axis in [0, 1]:
                for df in [frame, self.intframe]:
                    result = df.idxmin(axis=axis, skipna=skipna)
                    expected = df.apply(Series.idxmin, axis=axis,
                                        skipna=skipna)
                    tm.assert_series_equal(result, expected)

        pytest.raises(ValueError, frame.idxmin, axis=2)

    def test_idxmax(self):
        frame = self.frame
        frame.loc[5:10] = np.nan
        frame.loc[15:20, -2:] = np.nan
        for skipna in [True, False]:
            for axis in [0, 1]:
                for df in [frame, self.intframe]:
                    result = df.idxmax(axis=axis, skipna=skipna)
                    expected = df.apply(Series.idxmax, axis=axis,
                                        skipna=skipna)
                    tm.assert_series_equal(result, expected)

        pytest.raises(ValueError, frame.idxmax, axis=2)

    # ----------------------------------------------------------------------
    # Logical reductions

    def test_any_all(self):
        self._check_bool_op('any', np.any, has_skipna=True, has_bool_only=True)
        self._check_bool_op('all', np.all, has_skipna=True, has_bool_only=True)

        df = DataFrame(randn(10, 4)) > 0
        df.any(1)
        df.all(1)
        df.any(1, bool_only=True)
        df.all(1, bool_only=True)

        # skip pathological failure cases
        # class CantNonzero(object):

        #     def __nonzero__(self):
        #         raise ValueError

        # df[4] = CantNonzero()

        # it works!
        # df.any(1)
        # df.all(1)
        # df.any(1, bool_only=True)
        # df.all(1, bool_only=True)

        # df[4][4] = np.nan
        # df.any(1)
        # df.all(1)
        # df.any(1, bool_only=True)
        # df.all(1, bool_only=True)

    def _check_bool_op(self, name, alternative, frame=None, has_skipna=True,
                       has_bool_only=False):
        if frame is None:
            frame = self.frame > 0
            # set some NAs
            frame = DataFrame(frame.values.astype(object), frame.index,
                              frame.columns)
            frame.loc[5:10] = np.nan
            frame.loc[15:20, -2:] = np.nan

        f = getattr(frame, name)

        if has_skipna:
            def skipna_wrapper(x):
                nona = x.dropna().values
                return alternative(nona)

            def wrapper(x):
                return alternative(x.values)

            result0 = f(axis=0, skipna=False)
            result1 = f(axis=1, skipna=False)
            tm.assert_series_equal(result0, frame.apply(wrapper))
            tm.assert_series_equal(result1, frame.apply(wrapper, axis=1),
                                   check_dtype=False)  # HACK: win32
        else:
            skipna_wrapper = alternative
            wrapper = alternative

        result0 = f(axis=0)
        result1 = f(axis=1)
        tm.assert_series_equal(result0, frame.apply(skipna_wrapper))
        tm.assert_series_equal(result1, frame.apply(skipna_wrapper, axis=1),
                               check_dtype=False)

        # result = f(axis=1)
        # comp = frame.apply(alternative, axis=1).reindex(result.index)
        # assert_series_equal(result, comp)

        # bad axis
        pytest.raises(ValueError, f, axis=2)

        # make sure works on mixed-type frame
        mixed = self.mixed_frame
        mixed['_bool_'] = np.random.randn(len(mixed)) > 0
        getattr(mixed, name)(axis=0)
        getattr(mixed, name)(axis=1)

        class NonzeroFail:

            def __nonzero__(self):
                raise ValueError

        mixed['_nonzero_fail_'] = NonzeroFail()

        if has_bool_only:
            getattr(mixed, name)(axis=0, bool_only=True)
            getattr(mixed, name)(axis=1, bool_only=True)
            getattr(frame, name)(axis=0, bool_only=False)
            getattr(frame, name)(axis=1, bool_only=False)

        # all NA case
        if has_skipna:
            all_na = frame * np.NaN
            r0 = getattr(all_na, name)(axis=0)
            r1 = getattr(all_na, name)(axis=1)
            if name == 'any':
                assert not r0.any()
                assert not r1.any()
            else:
                assert r0.all()
                assert r1.all()

    # ----------------------------------------------------------------------
    # Isin

    def test_isin(self):
        # GH #4211
        df = DataFrame({'vals': [1, 2, 3, 4], 'ids': ['a', 'b', 'f', 'n'],
                        'ids2': ['a', 'n', 'c', 'n']},
                       index=['foo', 'bar', 'baz', 'qux'])
        other = ['a', 'b', 'c']

        result = df.isin(other)
        expected = DataFrame([df.loc[s].isin(other) for s in df.index])
        tm.assert_frame_equal(result, expected)

    def test_isin_empty(self):
        df = DataFrame({'A': ['a', 'b', 'c'], 'B': ['a', 'e', 'f']})
        result = df.isin([])
        expected = pd.DataFrame(False, df.index, df.columns)
        tm.assert_frame_equal(result, expected)

    def test_isin_dict(self):
        df = DataFrame({'A': ['a', 'b', 'c'], 'B': ['a', 'e', 'f']})
        d = {'A': ['a']}

        expected = DataFrame(False, df.index, df.columns)
        expected.loc[0, 'A'] = True

        result = df.isin(d)
        tm.assert_frame_equal(result, expected)

        # non unique columns
        df = DataFrame({'A': ['a', 'b', 'c'], 'B': ['a', 'e', 'f']})
        df.columns = ['A', 'A']
        expected = DataFrame(False, df.index, df.columns)
        expected.loc[0, 'A'] = True
        result = df.isin(d)
        tm.assert_frame_equal(result, expected)

    def test_isin_with_string_scalar(self):
        # GH4763
        df = DataFrame({'vals': [1, 2, 3, 4], 'ids': ['a', 'b', 'f', 'n'],
                        'ids2': ['a', 'n', 'c', 'n']},
                       index=['foo', 'bar', 'baz', 'qux'])
        with pytest.raises(TypeError):
            df.isin('a')

        with pytest.raises(TypeError):
            df.isin('aaa')

    def test_isin_df(self):
        df1 = DataFrame({'A': [1, 2, 3, 4], 'B': [2, np.nan, 4, 4]})
        df2 = DataFrame({'A': [0, 2, 12, 4], 'B': [2, np.nan, 4, 5]})
        expected = DataFrame(False, df1.index, df1.columns)
        result = df1.isin(df2)
        expected['A'].loc[[1, 3]] = True
        expected['B'].loc[[0, 2]] = True
        tm.assert_frame_equal(result, expected)

        # partial overlapping columns
        df2.columns = ['A', 'C']
        result = df1.isin(df2)
        expected['B'] = False
        tm.assert_frame_equal(result, expected)

    def test_isin_tuples(self):
        # GH16394
        df = pd.DataFrame({'A': [1, 2, 3], 'B': ['a', 'b', 'f']})
        df['C'] = list(zip(df['A'], df['B']))
        result = df['C'].isin([(1, 'a')])
        tm.assert_series_equal(result,
                               Series([True, False, False], name="C"))

    def test_isin_df_dupe_values(self):
        df1 = DataFrame({'A': [1, 2, 3, 4], 'B': [2, np.nan, 4, 4]})
        # just cols duped
        df2 = DataFrame([[0, 2], [12, 4], [2, np.nan], [4, 5]],
                        columns=['B', 'B'])
        with pytest.raises(ValueError):
            df1.isin(df2)

        # just index duped
        df2 = DataFrame([[0, 2], [12, 4], [2, np.nan], [4, 5]],
                        columns=['A', 'B'], index=[0, 0, 1, 1])
        with pytest.raises(ValueError):
            df1.isin(df2)

        # cols and index:
        df2.columns = ['B', 'B']
        with pytest.raises(ValueError):
            df1.isin(df2)

    def test_isin_dupe_self(self):
        other = DataFrame({'A': [1, 0, 1, 0], 'B': [1, 1, 0, 0]})
        df = DataFrame([[1, 1], [1, 0], [0, 0]], columns=['A', 'A'])
        result = df.isin(other)
        expected = DataFrame(False, index=df.index, columns=df.columns)
        expected.loc[0] = True
        expected.iloc[1, 1] = True
        tm.assert_frame_equal(result, expected)

    def test_isin_against_series(self):
        df = pd.DataFrame({'A': [1, 2, 3, 4], 'B': [2, np.nan, 4, 4]},
                          index=['a', 'b', 'c', 'd'])
        s = pd.Series([1, 3, 11, 4], index=['a', 'b', 'c', 'd'])
        expected = DataFrame(False, index=df.index, columns=df.columns)
        expected['A'].loc['a'] = True
        expected.loc['d'] = True
        result = df.isin(s)
        tm.assert_frame_equal(result, expected)

    def test_isin_multiIndex(self):
        idx = MultiIndex.from_tuples([(0, 'a', 'foo'), (0, 'a', 'bar'),
                                      (0, 'b', 'bar'), (0, 'b', 'baz'),
                                      (2, 'a', 'foo'), (2, 'a', 'bar'),
                                      (2, 'c', 'bar'), (2, 'c', 'baz'),
                                      (1, 'b', 'foo'), (1, 'b', 'bar'),
                                      (1, 'c', 'bar'), (1, 'c', 'baz')])
        df1 = DataFrame({'A': np.ones(12),
                         'B': np.zeros(12)}, index=idx)
        df2 = DataFrame({'A': [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1],
                         'B': [1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 1]})
        # against regular index
        expected = DataFrame(False, index=df1.index, columns=df1.columns)
        result = df1.isin(df2)
        tm.assert_frame_equal(result, expected)

        df2.index = idx
        expected = df2.values.astype(np.bool)
        expected[:, 1] = ~expected[:, 1]
        expected = DataFrame(expected, columns=['A', 'B'], index=idx)

        result = df1.isin(df2)
        tm.assert_frame_equal(result, expected)

    def test_isin_empty_datetimelike(self):
        # GH 15473
        df1_ts = DataFrame({'date':
                            pd.to_datetime(['2014-01-01', '2014-01-02'])})
        df1_td = DataFrame({'date':
                            [pd.Timedelta(1, 's'), pd.Timedelta(2, 's')]})
        df2 = DataFrame({'date': []})
        df3 = DataFrame()

        expected = DataFrame({'date': [False, False]})

        result = df1_ts.isin(df2)
        tm.assert_frame_equal(result, expected)
        result = df1_ts.isin(df3)
        tm.assert_frame_equal(result, expected)

        result = df1_td.isin(df2)
        tm.assert_frame_equal(result, expected)
        result = df1_td.isin(df3)
        tm.assert_frame_equal(result, expected)

    # ----------------------------------------------------------------------
    # Row deduplication

    def test_drop_duplicates(self):
        df = DataFrame({'AAA': ['foo', 'bar', 'foo', 'bar',
                                'foo', 'bar', 'bar', 'foo'],
                        'B': ['one', 'one', 'two', 'two',
                              'two', 'two', 'one', 'two'],
                        'C': [1, 1, 2, 2, 2, 2, 1, 2],
                        'D': lrange(8)})

        # single column
        result = df.drop_duplicates('AAA')
        expected = df[:2]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('AAA', keep='last')
        expected = df.loc[[6, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('AAA', keep=False)
        expected = df.loc[[]]
        tm.assert_frame_equal(result, expected)
        assert len(result) == 0

        # multi column
        expected = df.loc[[0, 1, 2, 3]]
        result = df.drop_duplicates(np.array(['AAA', 'B']))
        tm.assert_frame_equal(result, expected)
        result = df.drop_duplicates(['AAA', 'B'])
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates(('AAA', 'B'), keep='last')
        expected = df.loc[[0, 5, 6, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates(('AAA', 'B'), keep=False)
        expected = df.loc[[0]]
        tm.assert_frame_equal(result, expected)

        # consider everything
        df2 = df.loc[:, ['AAA', 'B', 'C']]

        result = df2.drop_duplicates()
        # in this case only
        expected = df2.drop_duplicates(['AAA', 'B'])
        tm.assert_frame_equal(result, expected)

        result = df2.drop_duplicates(keep='last')
        expected = df2.drop_duplicates(['AAA', 'B'], keep='last')
        tm.assert_frame_equal(result, expected)

        result = df2.drop_duplicates(keep=False)
        expected = df2.drop_duplicates(['AAA', 'B'], keep=False)
        tm.assert_frame_equal(result, expected)

        # integers
        result = df.drop_duplicates('C')
        expected = df.iloc[[0, 2]]
        tm.assert_frame_equal(result, expected)
        result = df.drop_duplicates('C', keep='last')
        expected = df.iloc[[-2, -1]]
        tm.assert_frame_equal(result, expected)

        df['E'] = df['C'].astype('int8')
        result = df.drop_duplicates('E')
        expected = df.iloc[[0, 2]]
        tm.assert_frame_equal(result, expected)
        result = df.drop_duplicates('E', keep='last')
        expected = df.iloc[[-2, -1]]
        tm.assert_frame_equal(result, expected)

        # GH 11376
        df = pd.DataFrame({'x': [7, 6, 3, 3, 4, 8, 0],
                           'y': [0, 6, 5, 5, 9, 1, 2]})
        expected = df.loc[df.index != 3]
        tm.assert_frame_equal(df.drop_duplicates(), expected)

        df = pd.DataFrame([[1, 0], [0, 2]])
        tm.assert_frame_equal(df.drop_duplicates(), df)

        df = pd.DataFrame([[-2, 0], [0, -4]])
        tm.assert_frame_equal(df.drop_duplicates(), df)

        x = np.iinfo(np.int64).max / 3 * 2
        df = pd.DataFrame([[-x, x], [0, x + 4]])
        tm.assert_frame_equal(df.drop_duplicates(), df)

        df = pd.DataFrame([[-x, x], [x, x + 4]])
        tm.assert_frame_equal(df.drop_duplicates(), df)

        # GH 11864
        df = pd.DataFrame([i] * 9 for i in range(16))
        df = df.append([[1] + [0] * 8], ignore_index=True)

        for keep in ['first', 'last', False]:
            assert df.duplicated(keep=keep).sum() == 0

    def test_drop_duplicates_for_take_all(self):
        df = DataFrame({'AAA': ['foo', 'bar', 'baz', 'bar',
                                'foo', 'bar', 'qux', 'foo'],
                        'B': ['one', 'one', 'two', 'two',
                              'two', 'two', 'one', 'two'],
                        'C': [1, 1, 2, 2, 2, 2, 1, 2],
                        'D': lrange(8)})

        # single column
        result = df.drop_duplicates('AAA')
        expected = df.iloc[[0, 1, 2, 6]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('AAA', keep='last')
        expected = df.iloc[[2, 5, 6, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('AAA', keep=False)
        expected = df.iloc[[2, 6]]
        tm.assert_frame_equal(result, expected)

        # multiple columns
        result = df.drop_duplicates(['AAA', 'B'])
        expected = df.iloc[[0, 1, 2, 3, 4, 6]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates(['AAA', 'B'], keep='last')
        expected = df.iloc[[0, 1, 2, 5, 6, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates(['AAA', 'B'], keep=False)
        expected = df.iloc[[0, 1, 2, 6]]
        tm.assert_frame_equal(result, expected)

    def test_drop_duplicates_tuple(self):
        df = DataFrame({('AA', 'AB'): ['foo', 'bar', 'foo', 'bar',
                                       'foo', 'bar', 'bar', 'foo'],
                        'B': ['one', 'one', 'two', 'two',
                              'two', 'two', 'one', 'two'],
                        'C': [1, 1, 2, 2, 2, 2, 1, 2],
                        'D': lrange(8)})

        # single column
        result = df.drop_duplicates(('AA', 'AB'))
        expected = df[:2]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates(('AA', 'AB'), keep='last')
        expected = df.loc[[6, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates(('AA', 'AB'), keep=False)
        expected = df.loc[[]]  # empty df
        assert len(result) == 0
        tm.assert_frame_equal(result, expected)

        # multi column
        expected = df.loc[[0, 1, 2, 3]]
        result = df.drop_duplicates((('AA', 'AB'), 'B'))
        tm.assert_frame_equal(result, expected)

    def test_drop_duplicates_NA(self):
        # none
        df = DataFrame({'A': [None, None, 'foo', 'bar',
                              'foo', 'bar', 'bar', 'foo'],
                        'B': ['one', 'one', 'two', 'two',
                              'two', 'two', 'one', 'two'],
                        'C': [1.0, np.nan, np.nan, np.nan, 1., 1., 1, 1.],
                        'D': lrange(8)})

        # single column
        result = df.drop_duplicates('A')
        expected = df.loc[[0, 2, 3]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('A', keep='last')
        expected = df.loc[[1, 6, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('A', keep=False)
        expected = df.loc[[]]  # empty df
        tm.assert_frame_equal(result, expected)
        assert len(result) == 0

        # multi column
        result = df.drop_duplicates(['A', 'B'])
        expected = df.loc[[0, 2, 3, 6]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates(['A', 'B'], keep='last')
        expected = df.loc[[1, 5, 6, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates(['A', 'B'], keep=False)
        expected = df.loc[[6]]
        tm.assert_frame_equal(result, expected)

        # nan
        df = DataFrame({'A': ['foo', 'bar', 'foo', 'bar',
                              'foo', 'bar', 'bar', 'foo'],
                        'B': ['one', 'one', 'two', 'two',
                              'two', 'two', 'one', 'two'],
                        'C': [1.0, np.nan, np.nan, np.nan, 1., 1., 1, 1.],
                        'D': lrange(8)})

        # single column
        result = df.drop_duplicates('C')
        expected = df[:2]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('C', keep='last')
        expected = df.loc[[3, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('C', keep=False)
        expected = df.loc[[]]  # empty df
        tm.assert_frame_equal(result, expected)
        assert len(result) == 0

        # multi column
        result = df.drop_duplicates(['C', 'B'])
        expected = df.loc[[0, 1, 2, 4]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates(['C', 'B'], keep='last')
        expected = df.loc[[1, 3, 6, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates(['C', 'B'], keep=False)
        expected = df.loc[[1]]
        tm.assert_frame_equal(result, expected)

    def test_drop_duplicates_NA_for_take_all(self):
        # none
        df = DataFrame({'A': [None, None, 'foo', 'bar',
                              'foo', 'baz', 'bar', 'qux'],
                        'C': [1.0, np.nan, np.nan, np.nan, 1., 2., 3, 1.]})

        # single column
        result = df.drop_duplicates('A')
        expected = df.iloc[[0, 2, 3, 5, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('A', keep='last')
        expected = df.iloc[[1, 4, 5, 6, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('A', keep=False)
        expected = df.iloc[[5, 7]]
        tm.assert_frame_equal(result, expected)

        # nan

        # single column
        result = df.drop_duplicates('C')
        expected = df.iloc[[0, 1, 5, 6]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('C', keep='last')
        expected = df.iloc[[3, 5, 6, 7]]
        tm.assert_frame_equal(result, expected)

        result = df.drop_duplicates('C', keep=False)
        expected = df.iloc[[5, 6]]
        tm.assert_frame_equal(result, expected)

    def test_drop_duplicates_inplace(self):
        orig = DataFrame({'A': ['foo', 'bar', 'foo', 'bar',
                                'foo', 'bar', 'bar', 'foo'],
                          'B': ['one', 'one', 'two', 'two',
                                'two', 'two', 'one', 'two'],
                          'C': [1, 1, 2, 2, 2, 2, 1, 2],
                          'D': lrange(8)})

        # single column
        df = orig.copy()
        df.drop_duplicates('A', inplace=True)
        expected = orig[:2]
        result = df
        tm.assert_frame_equal(result, expected)

        df = orig.copy()
        df.drop_duplicates('A', keep='last', inplace=True)
        expected = orig.loc[[6, 7]]
        result = df
        tm.assert_frame_equal(result, expected)

        df = orig.copy()
        df.drop_duplicates('A', keep=False, inplace=True)
        expected = orig.loc[[]]
        result = df
        tm.assert_frame_equal(result, expected)
        assert len(df) == 0

        # multi column
        df = orig.copy()
        df.drop_duplicates(['A', 'B'], inplace=True)
        expected = orig.loc[[0, 1, 2, 3]]
        result = df
        tm.assert_frame_equal(result, expected)

        df = orig.copy()
        df.drop_duplicates(['A', 'B'], keep='last', inplace=True)
        expected = orig.loc[[0, 5, 6, 7]]
        result = df
        tm.assert_frame_equal(result, expected)

        df = orig.copy()
        df.drop_duplicates(['A', 'B'], keep=False, inplace=True)
        expected = orig.loc[[0]]
        result = df
        tm.assert_frame_equal(result, expected)

        # consider everything
        orig2 = orig.loc[:, ['A', 'B', 'C']].copy()

        df2 = orig2.copy()
        df2.drop_duplicates(inplace=True)
        # in this case only
        expected = orig2.drop_duplicates(['A', 'B'])
        result = df2
        tm.assert_frame_equal(result, expected)

        df2 = orig2.copy()
        df2.drop_duplicates(keep='last', inplace=True)
        expected = orig2.drop_duplicates(['A', 'B'], keep='last')
        result = df2
        tm.assert_frame_equal(result, expected)

        df2 = orig2.copy()
        df2.drop_duplicates(keep=False, inplace=True)
        expected = orig2.drop_duplicates(['A', 'B'], keep=False)
        result = df2
        tm.assert_frame_equal(result, expected)

    # Rounding
    def test_round(self):
        # GH 2665

        # Test that rounding an empty DataFrame does nothing
        df = DataFrame()
        tm.assert_frame_equal(df, df.round())

        # Here's the test frame we'll be working with
        df = DataFrame({'col1': [1.123, 2.123, 3.123],
                        'col2': [1.234, 2.234, 3.234]})

        # Default round to integer (i.e. decimals=0)
        expected_rounded = DataFrame(
            {'col1': [1., 2., 3.], 'col2': [1., 2., 3.]})
        tm.assert_frame_equal(df.round(), expected_rounded)

        # Round with an integer
        decimals = 2
        expected_rounded = DataFrame({'col1': [1.12, 2.12, 3.12],
                                      'col2': [1.23, 2.23, 3.23]})
        tm.assert_frame_equal(df.round(decimals), expected_rounded)

        # This should also work with np.round (since np.round dispatches to
        # df.round)
        tm.assert_frame_equal(np.round(df, decimals), expected_rounded)

        # Round with a list
        round_list = [1, 2]
        with pytest.raises(TypeError):
            df.round(round_list)

        # Round with a dictionary
        expected_rounded = DataFrame(
            {'col1': [1.1, 2.1, 3.1], 'col2': [1.23, 2.23, 3.23]})
        round_dict = {'col1': 1, 'col2': 2}
        tm.assert_frame_equal(df.round(round_dict), expected_rounded)

        # Incomplete dict
        expected_partially_rounded = DataFrame(
            {'col1': [1.123, 2.123, 3.123], 'col2': [1.2, 2.2, 3.2]})
        partial_round_dict = {'col2': 1}
        tm.assert_frame_equal(df.round(partial_round_dict),
                              expected_partially_rounded)

        # Dict with unknown elements
        wrong_round_dict = {'col3': 2, 'col2': 1}
        tm.assert_frame_equal(df.round(wrong_round_dict),
                              expected_partially_rounded)

        # float input to `decimals`
        non_int_round_dict = {'col1': 1, 'col2': 0.5}
        with pytest.raises(TypeError):
            df.round(non_int_round_dict)

        # String input
        non_int_round_dict = {'col1': 1, 'col2': 'foo'}
        with pytest.raises(TypeError):
            df.round(non_int_round_dict)

        non_int_round_Series = Series(non_int_round_dict)
        with pytest.raises(TypeError):
            df.round(non_int_round_Series)

        # List input
        non_int_round_dict = {'col1': 1, 'col2': [1, 2]}
        with pytest.raises(TypeError):
            df.round(non_int_round_dict)

        non_int_round_Series = Series(non_int_round_dict)
        with pytest.raises(TypeError):
            df.round(non_int_round_Series)

        # Non integer Series inputs
        non_int_round_Series = Series(non_int_round_dict)
        with pytest.raises(TypeError):
            df.round(non_int_round_Series)

        non_int_round_Series = Series(non_int_round_dict)
        with pytest.raises(TypeError):
            df.round(non_int_round_Series)

        # Negative numbers
        negative_round_dict = {'col1': -1, 'col2': -2}
        big_df = df * 100
        expected_neg_rounded = DataFrame(
            {'col1': [110., 210, 310], 'col2': [100., 200, 300]})
        tm.assert_frame_equal(big_df.round(negative_round_dict),
                              expected_neg_rounded)

        # nan in Series round
        nan_round_Series = Series({'col1': nan, 'col2': 1})

        # TODO(wesm): unused?
        expected_nan_round = DataFrame({  # noqa
            'col1': [1.123, 2.123, 3.123],
            'col2': [1.2, 2.2, 3.2]})

        if sys.version < LooseVersion('2.7'):
            # Rounding with decimal is a ValueError in Python < 2.7
            with pytest.raises(ValueError):
                df.round(nan_round_Series)
        else:
            with pytest.raises(TypeError):
                df.round(nan_round_Series)

        # Make sure this doesn't break existing Series.round
        tm.assert_series_equal(df['col1'].round(1), expected_rounded['col1'])

        # named columns
        # GH 11986
        decimals = 2
        expected_rounded = DataFrame(
            {'col1': [1.12, 2.12, 3.12], 'col2': [1.23, 2.23, 3.23]})
        df.columns.name = "cols"
        expected_rounded.columns.name = "cols"
        tm.assert_frame_equal(df.round(decimals), expected_rounded)

        # interaction of named columns & series
        tm.assert_series_equal(df['col1'].round(decimals),
                               expected_rounded['col1'])
        tm.assert_series_equal(df.round(decimals)['col1'],
                               expected_rounded['col1'])

    def test_numpy_round(self):
        # See gh-12600
        df = DataFrame([[1.53, 1.36], [0.06, 7.01]])
        out = np.round(df, decimals=0)
        expected = DataFrame([[2., 1.], [0., 7.]])
        tm.assert_frame_equal(out, expected)

        msg = "the 'out' parameter is not supported"
        with tm.assert_raises_regex(ValueError, msg):
            np.round(df, decimals=0, out=df)

    def test_round_mixed_type(self):
        # GH11885
        df = DataFrame({'col1': [1.1, 2.2, 3.3, 4.4],
                        'col2': ['1', 'a', 'c', 'f'],
                        'col3': date_range('20111111', periods=4)})
        round_0 = DataFrame({'col1': [1., 2., 3., 4.],
                             'col2': ['1', 'a', 'c', 'f'],
                             'col3': date_range('20111111', periods=4)})
        tm.assert_frame_equal(df.round(), round_0)
        tm.assert_frame_equal(df.round(1), df)
        tm.assert_frame_equal(df.round({'col1': 1}), df)
        tm.assert_frame_equal(df.round({'col1': 0}), round_0)
        tm.assert_frame_equal(df.round({'col1': 0, 'col2': 1}), round_0)
        tm.assert_frame_equal(df.round({'col3': 1}), df)

    def test_round_issue(self):
        # GH11611

        df = pd.DataFrame(np.random.random([3, 3]), columns=['A', 'B', 'C'],
                          index=['first', 'second', 'third'])

        dfs = pd.concat((df, df), axis=1)
        rounded = dfs.round()
        tm.assert_index_equal(rounded.index, dfs.index)

        decimals = pd.Series([1, 0, 2], index=['A', 'B', 'A'])
        pytest.raises(ValueError, df.round, decimals)

    def test_built_in_round(self):
        if not compat.PY3:
            pytest.skip("build in round cannot be overriden "
                        "prior to Python 3")

        # GH11763
        # Here's the test frame we'll be working with
        df = DataFrame(
            {'col1': [1.123, 2.123, 3.123], 'col2': [1.234, 2.234, 3.234]})

        # Default round to integer (i.e. decimals=0)
        expected_rounded = DataFrame(
            {'col1': [1., 2., 3.], 'col2': [1., 2., 3.]})
        tm.assert_frame_equal(round(df), expected_rounded)

    # Clip

    def test_clip(self):
        median = self.frame.median().median()
        original = self.frame.copy()

        capped = self.frame.clip_upper(median)
        assert not (capped.values > median).any()

        floored = self.frame.clip_lower(median)
        assert not (floored.values < median).any()

        double = self.frame.clip(upper=median, lower=median)
        assert not (double.values != median).any()

        # Verify that self.frame was not changed inplace
        assert (self.frame.values == original.values).all()

    def test_inplace_clip(self):
        # GH #15388
        median = self.frame.median().median()
        frame_copy = self.frame.copy()

        frame_copy.clip_upper(median, inplace=True)
        assert not (frame_copy.values > median).any()
        frame_copy = self.frame.copy()

        frame_copy.clip_lower(median, inplace=True)
        assert not (frame_copy.values < median).any()
        frame_copy = self.frame.copy()

        frame_copy.clip(upper=median, lower=median, inplace=True)
        assert not (frame_copy.values != median).any()

    def test_dataframe_clip(self):
        # GH #2747
        df = DataFrame(np.random.randn(1000, 2))

        for lb, ub in [(-1, 1), (1, -1)]:
            clipped_df = df.clip(lb, ub)

            lb, ub = min(lb, ub), max(ub, lb)
            lb_mask = df.values <= lb
            ub_mask = df.values >= ub
            mask = ~lb_mask & ~ub_mask
            assert (clipped_df.values[lb_mask] == lb).all()
            assert (clipped_df.values[ub_mask] == ub).all()
            assert (clipped_df.values[mask] == df.values[mask]).all()

    @pytest.mark.xfail(reason=("clip on mixed integer or floats "
                               "with integer clippers coerces to float"))
    def test_clip_mixed_numeric(self):

        df = DataFrame({'A': [1, 2, 3],
                        'B': [1., np.nan, 3.]})
        result = df.clip(1, 2)
        expected = DataFrame({'A': [1, 2, 2],
                              'B': [1., np.nan, 2.]})
        tm.assert_frame_equal(result, expected, check_like=True)

    @pytest.mark.parametrize("inplace", [True, False])
    def test_clip_against_series(self, inplace):
        # GH #6966

        df = DataFrame(np.random.randn(1000, 2))
        lb = Series(np.random.randn(1000))
        ub = lb + 1

        original = df.copy()
        clipped_df = df.clip(lb, ub, axis=0, inplace=inplace)

        if inplace:
            clipped_df = df

        for i in range(2):
            lb_mask = original.iloc[:, i] <= lb
            ub_mask = original.iloc[:, i] >= ub
            mask = ~lb_mask & ~ub_mask

            result = clipped_df.loc[lb_mask, i]
            tm.assert_series_equal(result, lb[lb_mask], check_names=False)
            assert result.name == i

            result = clipped_df.loc[ub_mask, i]
            tm.assert_series_equal(result, ub[ub_mask], check_names=False)
            assert result.name == i

            tm.assert_series_equal(clipped_df.loc[mask, i], df.loc[mask, i])

    def test_clip_against_frame(self):
        df = DataFrame(np.random.randn(1000, 2))
        lb = DataFrame(np.random.randn(1000, 2))
        ub = lb + 1

        clipped_df = df.clip(lb, ub)

        lb_mask = df <= lb
        ub_mask = df >= ub
        mask = ~lb_mask & ~ub_mask

        tm.assert_frame_equal(clipped_df[lb_mask], lb[lb_mask])
        tm.assert_frame_equal(clipped_df[ub_mask], ub[ub_mask])
        tm.assert_frame_equal(clipped_df[mask], df[mask])

    def test_clip_na(self):
        msg = "Cannot use an NA"
        with tm.assert_raises_regex(ValueError, msg):
            self.frame.clip(lower=np.nan)

        with tm.assert_raises_regex(ValueError, msg):
            self.frame.clip(lower=[np.nan])

        with tm.assert_raises_regex(ValueError, msg):
            self.frame.clip(upper=np.nan)

        with tm.assert_raises_regex(ValueError, msg):
            self.frame.clip(upper=[np.nan])

        with tm.assert_raises_regex(ValueError, msg):
            self.frame.clip(lower=np.nan, upper=np.nan)

    # Matrix-like

    def test_dot(self):
        a = DataFrame(np.random.randn(3, 4), index=['a', 'b', 'c'],
                      columns=['p', 'q', 'r', 's'])
        b = DataFrame(np.random.randn(4, 2), index=['p', 'q', 'r', 's'],
                      columns=['one', 'two'])

        result = a.dot(b)
        expected = DataFrame(np.dot(a.values, b.values),
                             index=['a', 'b', 'c'],
                             columns=['one', 'two'])
        # Check alignment
        b1 = b.reindex(index=reversed(b.index))
        result = a.dot(b)
        tm.assert_frame_equal(result, expected)

        # Check series argument
        result = a.dot(b['one'])
        tm.assert_series_equal(result, expected['one'], check_names=False)
        assert result.name is None

        result = a.dot(b1['one'])
        tm.assert_series_equal(result, expected['one'], check_names=False)
        assert result.name is None

        # can pass correct-length arrays
        row = a.iloc[0].values

        result = a.dot(row)
        exp = a.dot(a.iloc[0])
        tm.assert_series_equal(result, exp)

        with tm.assert_raises_regex(ValueError,
                                    'Dot product shape mismatch'):
            a.dot(row[:-1])

        a = np.random.rand(1, 5)
        b = np.random.rand(5, 1)
        A = DataFrame(a)

        # TODO(wesm): unused
        B = DataFrame(b)  # noqa

        # it works
        result = A.dot(b)

        # unaligned
        df = DataFrame(randn(3, 4), index=[1, 2, 3], columns=lrange(4))
        df2 = DataFrame(randn(5, 3), index=lrange(5), columns=[1, 2, 3])

        with tm.assert_raises_regex(ValueError, 'aligned'):
            df.dot(df2)


@pytest.fixture
def df_duplicates():
    return pd.DataFrame({'a': [1, 2, 3, 4, 4],
                         'b': [1, 1, 1, 1, 1],
                         'c': [0, 1, 2, 5, 4]},
                        index=[0, 0, 1, 1, 1])


@pytest.fixture
def df_strings():
    return pd.DataFrame({'a': np.random.permutation(10),
                         'b': list(ascii_lowercase[:10]),
                         'c': np.random.permutation(10).astype('float64')})


@pytest.fixture
def df_main_dtypes():
    return pd.DataFrame(
        {'group': [1, 1, 2],
         'int': [1, 2, 3],
         'float': [4., 5., 6.],
         'string': list('abc'),
         'category_string': pd.Series(list('abc')).astype('category'),
         'category_int': [7, 8, 9],
         'datetime': pd.date_range('20130101', periods=3),
         'datetimetz': pd.date_range('20130101',
                                     periods=3,
                                     tz='US/Eastern'),
         'timedelta': pd.timedelta_range('1 s', periods=3, freq='s')},
        columns=['group', 'int', 'float', 'string',
                 'category_string', 'category_int',
                 'datetime', 'datetimetz',
                 'timedelta'])


class TestNLargestNSmallest(object):

    dtype_error_msg_template = ("Column {column!r} has dtype {dtype}, cannot "
                                "use method {method!r} with this dtype")

    # ----------------------------------------------------------------------
    # Top / bottom
    @pytest.mark.parametrize(
        'method, n, order',
        product(['nsmallest', 'nlargest'], range(1, 11),
                [['a'],
                 ['c'],
                 ['a', 'b'],
                 ['a', 'c'],
                 ['b', 'a'],
                 ['b', 'c'],
                 ['a', 'b', 'c'],
                 ['c', 'a', 'b'],
                 ['c', 'b', 'a'],
                 ['b', 'c', 'a'],
                 ['b', 'a', 'c'],

                 # dups!
                 ['b', 'c', 'c'],

                 ]))
    def test_n(self, df_strings, method, n, order):
        # GH10393
        df = df_strings
        if 'b' in order:

            error_msg = self.dtype_error_msg_template.format(
                column='b', method=method, dtype='object')
            with tm.assert_raises_regex(TypeError, error_msg):
                getattr(df, method)(n, order)
        else:
            ascending = method == 'nsmallest'
            result = getattr(df, method)(n, order)
            expected = df.sort_values(order, ascending=ascending).head(n)
            tm.assert_frame_equal(result, expected)

    @pytest.mark.parametrize(
        'method, columns',
        product(['nsmallest', 'nlargest'],
                product(['group'], ['category_string', 'string'])
                ))
    def test_n_error(self, df_main_dtypes, method, columns):
        df = df_main_dtypes
        error_msg = self.dtype_error_msg_template.format(
            column=columns[1], method=method, dtype=df[columns[1]].dtype)
        with tm.assert_raises_regex(TypeError, error_msg):
            getattr(df, method)(2, columns)

    def test_n_all_dtypes(self, df_main_dtypes):
        df = df_main_dtypes
        df.nsmallest(2, list(set(df) - {'category_string', 'string'}))
        df.nlargest(2, list(set(df) - {'category_string', 'string'}))

    def test_n_identical_values(self):
        # GH15297
        df = pd.DataFrame({'a': [1] * 5, 'b': [1, 2, 3, 4, 5]})

        result = df.nlargest(3, 'a')
        expected = pd.DataFrame(
            {'a': [1] * 3, 'b': [1, 2, 3]}, index=[0, 1, 2]
        )
        tm.assert_frame_equal(result, expected)

        result = df.nsmallest(3, 'a')
        expected = pd.DataFrame({'a': [1] * 3, 'b': [1, 2, 3]})
        tm.assert_frame_equal(result, expected)

    @pytest.mark.parametrize(
        'n, order',
        product([1, 2, 3, 4, 5],
                [['a', 'b', 'c'],
                 ['c', 'b', 'a'],
                 ['a'],
                 ['b'],
                 ['a', 'b'],
                 ['c', 'b']]))
    def test_n_duplicate_index(self, df_duplicates, n, order):
        # GH 13412

        df = df_duplicates
        result = df.nsmallest(n, order)
        expected = df.sort_values(order).head(n)
        tm.assert_frame_equal(result, expected)

        result = df.nlargest(n, order)
        expected = df.sort_values(order, ascending=False).head(n)
        tm.assert_frame_equal(result, expected)

    def test_series_broadcasting(self):
        # smoke test for numpy warnings
        # GH 16378, GH 16306
        df = DataFrame([1.0, 1.0, 1.0])
        df_nan = DataFrame({'A': [np.nan, 2.0, np.nan]})
        s = Series([1, 1, 1])
        s_nan = Series([np.nan, np.nan, 1])

        with tm.assert_produces_warning(None):
            df_nan.clip_lower(s, axis=0)
            for op in ['lt', 'le', 'gt', 'ge', 'eq', 'ne']:
                getattr(df, op)(s_nan, axis=0)