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Merged
merged 6 commits into from
Dec 22, 2021
Merged

Group by a categorical Series of unequal length #44180

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8d10ab4
CLN: Remove check for instance of Series performed by prior clause
stanwest Oct 25, 2021
08399e1
BUG: Group by categorical Series with unequal length GH44179
stanwest Oct 25, 2021
e8a0c9b
TST: Expand test of grouping by categorical Series
stanwest Oct 28, 2021
74580bf
DOC: Edit whatsnew entry for GH44179
stanwest Nov 8, 2021
65fcf42
CLN: Revise tests affected by fix for GH44179
stanwest Nov 8, 2021
b62a6f0
Merge upstream
stanwest Dec 8, 2021
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2 changes: 1 addition & 1 deletion doc/source/whatsnew/v1.4.0.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -593,7 +593,7 @@ Groupby/resample/rolling
- Fixed bug in :meth:`Series.rolling` and :meth:`DataFrame.rolling` for centered datetimelike windows with uneven nanosecond (:issue:`43997`)
- Bug in :meth:`GroupBy.nth` failing on ``axis=1`` (:issue:`43926`)
- Fixed bug in :meth:`Series.rolling` and :meth:`DataFrame.rolling` not respecting right bound on centered datetime-like windows, if the index contain duplicates (:issue:`#3944`)

- Enabled grouping by a :class:`Series` that has a categorical data type and length unequal to the axis of grouping (:issue:`44179`); also, with this fix, the ``ValueError`` raised when grouping by a :class:`Categorical` with unequal length now has the same message as when grouping by other sequences

Reshaping
^^^^^^^^^
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8 changes: 1 addition & 7 deletions pandas/core/groupby/grouper.py
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Expand Up @@ -887,12 +887,6 @@ def is_in_obj(gpr) -> bool:
else:
in_axis = False

if is_categorical_dtype(gpr) and len(gpr) != obj.shape[axis]:
raise ValueError(
f"Length of grouper ({len(gpr)}) and axis ({obj.shape[axis]}) "
"must be same length"
)

# create the Grouping
# allow us to passing the actual Grouping as the gpr
ping = (
Expand Down Expand Up @@ -938,7 +932,7 @@ def _convert_grouper(axis: Index, grouper):
return grouper.reindex(axis)._values
elif isinstance(grouper, MultiIndex):
return grouper._values
elif isinstance(grouper, (list, tuple, Series, Index, np.ndarray)):
elif isinstance(grouper, (list, tuple, Index, Categorical, np.ndarray)):
if len(grouper) != len(axis):
raise ValueError("Grouper and axis must be same length")

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9 changes: 7 additions & 2 deletions pandas/tests/groupby/test_categorical.py
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Expand Up @@ -668,11 +668,16 @@ def test_bins_unequal_len():
bins = pd.cut(series.dropna().values, 4)

# len(bins) != len(series) here
msg = r"Length of grouper \(8\) and axis \(10\) must be same length"
with pytest.raises(ValueError, match=msg):
with pytest.raises(ValueError, match=r"Grouper and axis must be same length"):
series.groupby(bins).mean()


def test_categorical_series_unequal_len():
# GH44179
groupby = Series(range(7)).groupby(Series(list("ABBA"), dtype="category"))
tm.assert_dict_equal(groupby.groups, {"A": [0, 3], "B": [1, 2]})


def test_as_index():
# GH13204
df = DataFrame(
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