CODEWITHSUNDEEP
pythonpandasnumpy
hcp
hcp

Reputation: 347

Indexing Error while trying to locate index where condition is satisfied

I'm trying to locate the indexes of a variable where a condition is given. 

df.loc[df.variable[mask].diff() == 1]

But when I write it, it returns me an odd error 

IndexingError: Unalignable boolean Series provided as indexer (index of the boolean Series and of the indexed object do not match).

the variable is a series of boolean values and the mask is just an interval like this:

mask = df.time_var.dt.date == datetime.date(2019, 10, 22)

what am I doing wrong?

Upvotes: 1

Views: 128

Answers (1)

V. Ayrat
V. Ayrat

Reputation: 2719

import pandas as pd


df = pd.DataFrame([[1, 2], [3, 4], [5, 6]])
print(df)
   # 0  1
# 0  1  2
# 1  3  4
# 2  5  6
print(df.loc[pd.Series([True, False, True])])
   # 0  1
# 0  1  2
# 2  5  6
print(df.loc[pd.Series([True, False])])
# Traceback (most recent call last):
# pandas.core.indexing.IndexingError: Unalignable boolean Series provided as indexer (index of the boolean Series and of the indexed object do not match).

df.variable[mask].diff() == 1 is boolean Series which has different length than df so pandas can not decide which rows to choose. You probably can use this:

df.loc[(df.variable[mask].diff() == 1).index]

Upvotes: 1

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