pandas-dev/pandas (original) (raw)

Hi, thanks to all of you who spend time on this project, it is invaluable to me.
Unfortuatnely, i think I have run into an indexing-type issue, either that or my expectations are incorrect. Consider the following script:

import random import pandas import numpy as np

columns = list('abcdefg') subcols = columns[1:-1] X = pandas.DataFrame(0.0, columns=columns, index=range(100)) Z = pandas.DataFrame(np.random.randn(100,len(subcols)), columns=subcols, index=range(100)) block1 = list(subcols) random.shuffle(block1)

X[block1] -= Z print X.corrwith(Z)

X = pandas.DataFrame(0.0, columns=columns, index=range(100)) X[block1] -= Z[block1] print X.corrwith(Z)

print pandas.version

The output i get is something like this (obviously depends on the random inputs)
a NaN
b -0.127386
c -0.073521
d -0.073521
e -0.127386
f -1.000000
g NaN
dtype: float64
a NaN
b -1
c -1
d -1
e -1
f -1
g NaN
dtype: float64
0.15.0rc1-10-g215569a

where the second result is what i would have expected.
I was surprised to find that I have to "reindex" Z by block1 to get a correct result. Is my expectation incorrect?

Many thanks