BUG: freq set to NONE when resampling pd.Multiindex (introduced in v1.1.0) · Issue #35563 · pandas-dev/pandas (original) (raw)

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Update/Summary

When dealing with a pd.multiindex the frequency df.loc[i].index.freq has not been set. This behavior has been introduced in v1.1.0

idx = pd.Index(range(2), name="A")
dti = pd.date_range("2020-01-01", periods=7, freq="D", name="B")
mi = pd.MultiIndex.from_product([idx, dti])

df = pd.DataFrame(np.random.randn(14, 2), index=mi)

>>> df.loc[0].index

df.loc[0].index matches dti, so it would be nice to get the freq="D" back on that.

using code sample in #35563 (comment) points to #31315

c988567 is the first bad commit
commit c988567
Author: jbrockmendel jbrockmendel@gmail.com
Date: Sun Feb 9 07:01:20 2020 -0800

REF: tighten what we accept in TimedeltaIndex._simple_new (#31315)

Original post

Code Sample, a copy-pastable example

import numpy as np import pandas as pd

idx_level_0 = np.repeat([1, 2], 5) dates = np.tile( ["2020-01-01", "2020-01-02", "2020-01-04", "2020-01-06", "2020-01-07"], 2 ) values1 = [1, 2, 3, 4, 5] values2 = [6, 7, 8, 9, 10]

df = pd.DataFrame( {"idx_level_0": idx_level_0, "dates": dates, "values": [*values1, *values2]} ) df["dates"] = pd.to_datetime(df["dates"]) df = df.set_index(["idx_level_0", "dates"], drop=True)

df = df.groupby("idx_level_0").resample("D", level="dates").last()

The following assertion is working properly in pandas v1.0.5

It throws an error in pandas v1.1.0

assert df.index.get_level_values(1).freq == "D"

Problem description

When resampling a groupby-object, the frequency will incorrectly be set to None.

Expected Output

The frequency should be set according to the resampled frequency.

Output of pd.show_versions()

INSTALLED VERSIONS

commit : d9fff27
python : 3.8.2.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.19041
machine : AMD64
processor : Intel64 Family 6 Model 60 Stepping 3, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : de_DE.cp1252
pandas : 1.1.0
numpy : 1.18.4
pytz : 2020.1
dateutil : 2.8.1
pip : 20.1.1
setuptools : 45.3.0
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : 4.5.1
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : None
IPython : None
pandas_datareader: None
bs4 : None
bottleneck : None
fsspec : None
fastparquet : None
gcsfs : None
matplotlib : 3.2.2
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pytables : None
pyxlsb : None
s3fs : None
scipy : 1.5.0
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
numba : None