[Numpy-discussion] Slicing with index lists
Bernhard Voigt
bernhard.voigt at gmail.com
Thu Apr 12 04:35:01 EDT 2007
Dear all!
in a 2-dim array I would like to select rows specified by a list of indexes
and from these rows I'd like to select columns specified by another list of
indexes. That's what I found as a solution:
In [90]: a = arange(15).reshape(5,3)
In [91]: a
Out[91]:
array([[ 0, 1, 2],
[ 3, 4, 5],
[ 6, 7, 8],
[ 9, 10, 11],
[12, 13, 14]])
# select rows 1,3,4 and columns 0,2
In[92]: a[[1,3,4],:][:,[0,2]]
Out[92]:
array([[ 3, 5],
[ 9, 11],
[12, 14]])
Is there a better way to express this selection? I thought there might be
single slicing expression for this, but I couldn't figure it out :-(
I tried:
In [97]: a[[1,3,4],[0,2]]
---------------------------------------------------------------------------
exceptions.ValueError Traceback (most recent
call last)
ValueError: shape mismatch: objects cannot be broadcast to a single shape
Thanks for help! Bernhard
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