Month: December 2015

Mixed indexing with integer index in Pandas DataFrame

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Indexing in Python’s Pandas can at times be tricky. Here is an example with mixed indexing (.ix) with integer index:


import pandas as pd
df = pd.DataFrame([[1, 2, 's'], [3, 4, 't'], [4, 5, 'u']],
index=[-1, 0, 1], columns=['a', 'b', 'c'])
>>> df.a # Correct type
-1 1
0 3
1 4
Name: a, dtype: int64
>>> df.loc[0, ['a', 'b']] # Wrong indexing
a 3
b 4
Name: 0, dtype: object
>>> df.ix[0, ['a', 'b']] # Wrong indexing
a 3
b 4
Name: 0, dtype: object
>>> df.iloc[0, :][['a', 'b']] # Correct indexing, wrong type
a 1
b 2
Name: -1, dtype: object
>>> df.loc[:, ['a', 'b']].iloc[0, :] # Correct indexing and type, but long
a 1
b 2
Name: -1, dtype: int64
>>> df.ix[df.index[0], ['a', 'b']] # Ok
a 1
b 2

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mixedindexing.py

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I ran into the issue when I wanted index with integer for DataFrame representing EEG data in one of its methods

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