Re: numpy problem

From	Michael Selik <michael.selik@gmail.com>
Newsgroups	comp.lang.python
Subject	Re: numpy problem
Date	2016-05-23 23:00 +0000
Message-ID	<mailman.37.1464044443.20402.python-list@python.org> (permalink)
References	<46F1751E-CA1E-4AB3-B6EB-589E1E2FD1D9@onemanifest.net> <nhusgg$vna$1@ger.gmane.org> <17D9C96A-C4EB-426F-A4A7-AA6492D7DBAB@onemanifest.net> <CAGgTfkPR2FMuKW6j5DrowYT5ML4prG8z1=8qhhviW4Z-K8WkoQ@mail.gmail.com>

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On Mon, May 23, 2016 at 9:12 AM <lists@onemanifest.net> wrote:

> > On 23 mei 2016, at 14:19, Peter Otten <__peter__@web.de> wrote:
> > lists@onemanifest.net wrote:
> >
> >> I've got a 2D array
> >> And an array of indexes that for shows which row to keep for each column
> >> of values:
> >>
> >> keep = np.array([2, 3, 1, 9, 2])
> >>
> >> So, the result should be an array like array([ values[2,0], values[3,1],
> >> values[1,2], values[9,3], values[2,4] ]) == np.array([92, 62, 38, 81,
> 44])
> >>
> > values[keep].diagonal()
>
> That seems to do the trick!
>

To clarify, the fancy index is selecting all rows you want to keep, which
gives you a 5x5 array (repeating rows if necessary). Then you are getting
the diagonal of that selection.

If that was already clear, my apologies for the noise.

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Re: numpy problem Michael Selik <michael.selik@gmail.com> - 2016-05-23 23:00 +0000

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