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Fix bug in multiindex series groupby where sort argument is ignored #9461

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Merged
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Feb 11, 2015
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Fix bug in multiindex series groupby where sort argument is ignored #9461

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1 change: 1 addition & 0 deletions doc/source/whatsnew/v0.16.0.txt
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Expand Up @@ -268,3 +268,4 @@ Bug Fixes

- Bug in ``read_csv`` with buffer overflows with certain malformed input files (:issue:`9205`)
- Bug in groupby MultiIndex with missing pair (:issue:`9049`, :issue:`9344`)
- Fixed bug in ``Series.groupby`` where grouping on ``MultiIndex`` levels would ignore the sort argument (:issue:`9444`)
2 changes: 1 addition & 1 deletion pandas/core/groupby.py
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Expand Up @@ -1368,7 +1368,7 @@ def _get_compressed_labels(self):
if len(all_labels) > 1:
group_index = get_group_index(all_labels, self.shape,
sort=True, xnull=True)
return _compress_group_index(group_index)
return _compress_group_index(group_index, sort=self.sort)

ping = self.groupings[0]
return ping.labels, np.arange(len(ping.group_index))
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17 changes: 17 additions & 0 deletions pandas/tests/test_groupby.py
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Expand Up @@ -3270,6 +3270,23 @@ def test_no_dummy_key_names(self):
self.df['B'].values]).sum()
self.assertEqual(result.index.names, (None, None))

def test_groupby_sort_multiindex_series(self):
# series multiindex groupby sort argument was not being passed through _compress_group_index
# GH 9444
index = MultiIndex(levels=[[1, 2], [1, 2]],
labels=[[0, 0, 0, 0, 1, 1], [1, 1, 0, 0, 0, 0]],
names=['a', 'b'])
mseries = Series([0, 1, 2, 3, 4, 5], index=index)
index = MultiIndex(levels=[[1, 2], [1, 2]],
labels=[[0, 0, 1], [1, 0, 0]],
names=['a', 'b'])
mseries_result = Series([0, 2, 4], index=index)

result = mseries.groupby(level=['a', 'b'], sort=False).first()
assert_series_equal(result, mseries_result)
result = mseries.groupby(level=['a', 'b'], sort=True).first()
assert_series_equal(result, mseries_result.sort_index())

def test_groupby_categorical(self):
levels = ['foo', 'bar', 'baz', 'qux']
codes = np.random.randint(0, 4, size=100)
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