[Numpy-discussion] Indexing 2d arrays by column using an integer array
William Furnass
will@thearete.co...
Mon Feb 13 13:26:44 CST 2012
Hi,
Apologies if the following is a trivial question. I wish to index the
columns of the following 2D array
In [78]: neighbourhoods
Out[78]:
array([[8, 0, 1],
[0, 1, 2],
[1, 2, 3],
[2, 3, 4],
[3, 4, 5],
[4, 5, 6],
[5, 6, 7],
[6, 7, 8],
[7, 8, 0]])
using the integer array
In [76]: perf[neighbourhoods].argmax(axis=1)
Out[76]: array([2, 1, 0, 2, 1, 0, 0, 2, 1])
to produce a 9-element array but can't find a way of applying the
indices to the columns rather than the rows. Is this do-able without
using loops?
The looped version of what I want is
np.array( [neighbourhoods[i][perf[neighbourhoods].argmax(axis=1)[i]]
for i in xrange(neighbourhoods.shape[0])] )
Regards,
--
Will Furnass
Doctoral Student
Pennine Water Group
Department of Civil and Structural Engineering
University of Sheffield
Phone: +44 (0)114 22 25768
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