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BUG: subset parameter of DataFrameGroupBy.value_counts has no effect #46383

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LucasG0 opened this issue Mar 15, 2022 · 4 comments · Fixed by #48164
Closed
3 tasks done

BUG: subset parameter of DataFrameGroupBy.value_counts has no effect #46383

LucasG0 opened this issue Mar 15, 2022 · 4 comments · Fixed by #48164
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@zhenqin77
Labels
Algos Non-arithmetic algos: value_counts, factorize, sorting, isin, clip, shift, diff Bug Groupby
Milestone
1.4.4

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@LucasG0
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LucasG0 commented Mar 15, 2022 •
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Pandas version checks

  • I have checked that this issue has not already been reported.

  • I have confirmed this bug exists on the latest version of pandas.

  • I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

>>> df = pd.DataFrame({"c1": ["a", "b", "c"], "c2": ["x", "y", "y"]}, index=[0, 1, 1])
>>> df
  c1 c2
0  a  x
1  b  y
1  c  y
>>> df.groupby(level=0).value_counts(subset=["c2"])
   c1  c2
0  a   x     1
1  b   y     1
   c   y     1
dtype: int64                                                                                                             dtype: int64

Issue Description

subset has no effect. Within the code, there is only a check that subset and grouping keys do not intersect.

Expected Behavior

Keeps only subset columns for counting unique combinations and drop the other columns.

>>> df.groupby(level=0).value_counts(subset=["c2"])
   c2
0  x     1
1  y     2
dtype: int64

So it is consistent with DataFrame.value_counts:

>>> df.value_counts(subset=["c2"])
c2
y     2
x     1
dtype: int64

In practice, this is equivalent of using df.groupby(level=0)[["c2"]].value_counts().

Installed Versions

INSTALLED VERSIONS

commit : 06d2301
python : 3.9.1.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.19041
machine : AMD64
processor : Intel64 Family 6 Model 142 Stepping 11, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : fr_FR.cp1252

pandas : 1.4.1
numpy : 1.20.1
pytz : 2021.1
dateutil : 2.8.1
pip : 20.3.3
setuptools : 52.0.0.post20210125
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.0.3
IPython : 8.1.1
pandas_datareader: None
bs4 : None
bottleneck : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : None
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
zstandard : None
@LucasG0 LucasG0 added Bug Needs Triage Issue that has not been reviewed by a pandas team member labels Mar 15, 2022
@mroeschke mroeschke added Groupby Algos Non-arithmetic algos: value_counts, factorize, sorting, isin, clip, shift, diff and removed Needs Triage Issue that has not been reviewed by a pandas team member labels Mar 17, 2022
@gpapadok
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@gpapadok gpapadok mentioned this issue Mar 20, 2022
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@gpapadok gpapadok removed their assignment Mar 22, 2022
@zhenqin77
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@DongqiWu DongqiWu mentioned this issue Apr 23, 2022
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@weikhor weikhor mentioned this issue May 1, 2022
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@weikhor
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weikhor commented May 1, 2022 •
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Sorry. I do not know there is already another pull request exists. I already close my PR.

@simonjayhawkins
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Thanks @LucasG0 for the report.

DataFrameGroupBy.value_counts added in pandas-1.4.0 (#43564). cc @corriebar

adding a 1.4.x milestone as any fix could be considered a backport candidate.

contributions and PRs welcome.

@simonjayhawkins simonjayhawkins added this to the 1.4.3 milestone Jun 10, 2022
@simonjayhawkins simonjayhawkins modified the milestones: 1.4.3, 1.4.4 Jun 22, 2022
@mroeschke mroeschke mentioned this issue Aug 19, 2022
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Labels
Algos Non-arithmetic algos: value_counts, factorize, sorting, isin, clip, shift, diff Bug Groupby
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Milestone
1.4.4
6 participants
@mroeschke @simonjayhawkins @weikhor @gpapadok @LucasG0 @zhenqin77