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Re: how to create a permutation matrix
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From: |
Jordi Gutiérrez Hermoso |
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Subject: |
Re: how to create a permutation matrix |
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Date: |
Mon, 26 Jan 2015 13:57:42 -0500 |
On Mon, 2015-01-26 at 18:58 +0100, c. wrote:
> Is it expected that :
>
> >> P = eye (4);
> >> P = P([2 1 3 4], :);
> >> typeinfo (P)
> ans = permutation matrix
>
> but
>
> >> P = eye (4);
> >> P ([1 2], :) = P([2 1], :);
> >> typeinfo (P)
> ans = matrix
Yes, that's the current implementation. You need to specify the full
permutation vector in order to get a permutation matrix. It would take
a bit more magic to realise that P([2 1], :) is being assigned to a
permuted version of itself and thus create a permutation matrix.
- Jordi G. H.