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## Re: how to create a permutation matrix

**From**: |
c. |

**Subject**: |
Re: how to create a permutation matrix |

**Date**: |
Mon, 26 Jan 2015 18:58:47 +0100 |

On 26 Jan 2015, at 18:35, Jordi Gutiérrez Hermoso <address@hidden> wrote:
>* On Mon, 2015-01-26 at 17:57 +0100, c. wrote:*
>*>>> [l, u, p] = lu (a' * a);*
>*>>> typeinfo (p)*
>*> ans = permutation matrix*
>*> *
>*> is there a way to create an object of his type in an m-file?*
>* *
>* *
>* https://www.gnu.org/software/octave/doc/interpreter/Creating-Permutation-Matrices.html*
>* *
>* HTH,*
>* - Jordi G. H.*
Thanks,
That was exactly what I was looking for, I knew it was somewhere but I forgot
where ;)
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
BTW the reason I was asking is that I was trying to implement this algorithm
[1] in
an m-file (see attachment).
Does anyone else need this? If so maybe I could commit it to the linear-algebra
package?
c.
[1]
http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatReorderForNonzeroDiagonal.html

**
**`reorder_for_nonzero_diagonal.m`

*Description:* Binary data