[Numpy-discussion] how to use argsort result?

Pau Gargallo pau.gargallo at gmail.com
Tue Jul 11 04:40:44 CDT 2006


here goes a first try:

A[arange(2)[:,newaxis],indexes]


pau

On 7/11/06, Emanuele Olivetti <olivetti at itc.it> wrote:
> Hi,
> I don't understand how to use argsort results. I have a 2D matrix and
> I want to sort values in each row and obtain the index array of that
> sorting. Argsort(1) is what I need, but the problem is how to use its
> result in order to obtain a sorted matrix. Here is the simple example:
>
> A = array([[2,3,1],[5,4,6]])
> indexes = a.argsort(1)
>
> now indexes is:
> array([[2, 0, 1],
>         [1, 0, 2]])
>
> I'd like to apply indexes to A and obtain:
> array([[1, 2, 3],
>         [4, 5, 6]])
>
> or better, I'm interested both in a subset of indexes, i.e. indexes[:,1:], and
> the related values of A matrix.
>
> How can I do this? If I simpy say: A[indexes] I get an IndexError.
>
> Thanks in advance,
>
> Emanuele
>
> P.S. numpy.__version__ is '0.9.8'.
>
>
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