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BUG: Period resample with length=0 doesn't set freq #13067

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BUG: Period resample with length=0 doesn't set freq #13067

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2 changes: 2 additions & 0 deletions doc/source/whatsnew/v0.18.2.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -74,3 +74,5 @@ Performance Improvements

Bug Fixes
~~~~~~~~~

- Bug in ``.resample`` empty data with ``PeriodIndex`` doesn't change ``freq`` (:issue:`13067`)
5 changes: 4 additions & 1 deletion pandas/tseries/resample.py
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Expand Up @@ -790,7 +790,10 @@ def _downsample(self, how, **kwargs):

new_index = self._get_new_index()
if len(new_index) == 0:
return self._wrap_result(self._selected_obj.reindex(new_index))
result = self._selected_obj
if isinstance(self._selected_obj.index, PeriodIndex):
result = result.asfreq(self.freq, how=self.convention)
return self._wrap_result(result.reindex(new_index))

# Start vs. end of period
memb = ax.asfreq(self.freq, how=self.convention)
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13 changes: 7 additions & 6 deletions pandas/tseries/tests/test_resample.py
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Expand Up @@ -2043,17 +2043,18 @@ def test_resample_basic(self):
assert_series_equal(result2, expected)

def test_resample_empty(self):

# GH12771 & GH12868
index = PeriodIndex(start='2000', periods=0, freq='D', name='idx')
s = Series(index=index)

expected_index = PeriodIndex([], name='idx', freq='M')
expected = Series(index=expected_index)
for freq in ['M', 'D', 'H']:
expected_index = PeriodIndex([], name='idx', freq=freq)
expected = Series(index=expected_index)

for method in resample_methods:
result = getattr(s.resample('M'), method)()
assert_series_equal(result, expected)
for method in resample_methods:
result = getattr(s.resample(freq), method)()
assert_series_equal(result, expected)
self.assertEqual(result.index.freq, freq)

def test_resample_count(self):

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