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BUG: .max() gives wrong answer for non-nanosecond datetimeindex #50719

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Merged
merged 5 commits into from
Jan 13, 2023
Merged

BUG: .max() gives wrong answer for non-nanosecond datetimeindex #50719

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93253eb
fix max non-nano
Jan 12, 2023
cdaca2c
match dtype in NaT case too
Jan 13, 2023
b242b1c
Merge remote-tracking branch 'upstream/main' into fix-non-nano-max
Jan 13, 2023
228d7c1
check unit in test
Jan 13, 2023
3c8c4ae
Merge branch 'main' into fix-non-nano-max
MarcoGorelli Jan 13, 2023
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2 changes: 1 addition & 1 deletion pandas/core/nanops.py
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Original file line number Diff line number Diff line change
Expand Up @@ -372,7 +372,7 @@ def _wrap_results(result, dtype: np.dtype, fill_value=None):
if isna(result):
result = np.datetime64("NaT", "ns")
else:
result = np.int64(result).view("datetime64[ns]")
result = np.int64(result).view(dtype)
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can you do the nat case a couple lines up too just to be on the safe side (like we do for td64 below)

# retain original unit
result = result.astype(dtype, copy=False)
else:
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13 changes: 9 additions & 4 deletions pandas/tests/test_nanops.py
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Expand Up @@ -1157,10 +1157,14 @@ def prng(self):


class TestDatetime64NaNOps:
@pytest.fixture(params=["s", "ms", "us", "ns"])
def unit(self, request):
return request.param

# Enabling mean changes the behavior of DataFrame.mean
# See https://github.com/pandas-dev/pandas/issues/24752
def test_nanmean(self):
dti = pd.date_range("2016-01-01", periods=3)
def test_nanmean(self, unit):
dti = pd.date_range("2016-01-01", periods=3).as_unit(unit)
expected = dti[1]

for obj in [dti, DatetimeArray(dti), Series(dti)]:
Expand All @@ -1173,8 +1177,9 @@ def test_nanmean(self):
result = nanops.nanmean(obj)
assert result == expected

@pytest.mark.parametrize("dtype", ["M8[ns]", "m8[ns]"])
def test_nanmean_skipna_false(self, dtype):
@pytest.mark.parametrize("constructor", ["M8", "m8"])
def test_nanmean_skipna_false(self, constructor, unit):
dtype = f"{constructor}[{unit}]"
arr = np.arange(12).astype(np.int64).view(dtype).reshape(4, 3)

arr[-1, -1] = "NaT"
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