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BUG: remove_unused_categories with NaN values (GH11599) #11639

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Merged
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Nov 18, 2015
Merged

BUG: remove_unused_categories with NaN values (GH11599) #11639

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1 change: 1 addition & 0 deletions doc/source/whatsnew/v0.17.1.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -187,3 +187,4 @@ Bug Fixes
- Bug in ``DataFrame.join()`` with ``how='right'`` producing a ``TypeError`` (:issue:`11519`)
- Bug in ``Series.quantile`` with empty list results has ``Index`` with ``object`` dtype (:issue:`11588`)
- Bug in ``pd.merge`` results in empty ``Int64Index`` rather than ``Index(dtype=object)`` when the merge result is empty (:issue:`11588`)
- Bug in ``remove_unused_categories`` when having ``NaN`` values (:issue:`11599`).
3 changes: 3 additions & 0 deletions pandas/core/categorical.py
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Expand Up @@ -817,6 +817,9 @@ def remove_unused_categories(self, inplace=False):
"""
cat = self if inplace else self.copy()
_used = sorted(np.unique(cat._codes))
if _used[0] == -1:
_used = _used[1:]

new_categories = cat.categories.take(_ensure_platform_int(_used))

from pandas.core.index import _ensure_index
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5 changes: 5 additions & 0 deletions pandas/tests/test_categorical.py
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Expand Up @@ -844,6 +844,11 @@ def test_remove_unused_categories(self):
self.assert_numpy_array_equal(c.categories, exp_categories_dropped)
self.assertIsNone(res)

# with NaN values (GH11599)
c = Categorical(["a","b","c",np.nan], categories=["a","b","c","d","e"])
res = c.remove_unused_categories()
self.assert_numpy_array_equal(res.categories, np.array(["a","b","c"]))
self.assert_numpy_array_equal(c.categories, exp_categories_all)

def test_nan_handling(self):

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