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FIX DataFrame diff with timedelta #7280

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FIX DataFrame diff with timedelta #7280

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3 changes: 2 additions & 1 deletion pandas/core/common.py
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Original file line number Diff line number Diff line change
Expand Up @@ -813,7 +813,8 @@ def diff(arr, n, axis=0):
na_indexer[axis] = slice(None, n) if n >= 0 else slice(n, None)
out_arr[tuple(na_indexer)] = na

if arr.ndim == 2 and arr.dtype.name in _diff_special:
if (arr.ndim == 2 and arr.dtype.name in _diff_special
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actually I would do this slightly differently. I would define the dtype of out_arr (as the same as the input type), except for datetime64[ns], then I think you can use this as is.

and dtype != 'timedelta64[ns]'):
f = _diff_special[arr.dtype.name]
f(arr, out_arr, n, axis)
else:
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10 changes: 10 additions & 0 deletions pandas/tests/test_frame.py
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Expand Up @@ -9285,6 +9285,16 @@ def test_diff_float_n(self):
xp = self.tsframe.diff(1)
assert_frame_equal(rs, xp)

def test_diff_timedelta(self):
df = DataFrame(dict(time=[Timestamp('20130101 9:01'),
Timestamp('20130101 9:02')],
value=[1.0,2.0]))
res = df.diff()
exp = DataFrame([[pd.NaT, np.nan],
[np.timedelta64(int(6e10), 'ns'), 1]],
columns=['time', 'value'])
assert_frame_equal(res, exp)

def test_pct_change(self):
rs = self.tsframe.pct_change(fill_method=None)
assert_frame_equal(rs, self.tsframe / self.tsframe.shift(1) - 1)
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