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## Re: indexed assignment for sparse matrices in ov-2.9.4

 From: David Bateman Subject: Re: indexed assignment for sparse matrices in ov-2.9.4 Date: Thu, 19 Jan 2006 17:29:00 +0100 User-agent: Mozilla Thunderbird 1.0.2 (Windows/20050317)

```Thomas Kasper a écrit :

```
```Hi,

I have a problem with indexed assignment for sparse matrices in
octave-2.9.4. See below for an example:

octave:1> version
ans = 2.9.4
octave:2> a = sparse(eye(3))
a =

Compressed Column Sparse (rows = 3, cols = 3, nnz = 3)

(1, 1) -> 1
(2, 2) -> 1
(3, 3) -> 1

octave:3> a(:,[3,2,1]) = a
a =

Compressed Column Sparse (rows = 3, cols = 3, nnz = 3)

(1, 1) -> 1
(2, 2) -> 1
(3, 3) -> 1

```
Firstly, you should use speye(n) rather than sparse(eye(n)) as the full n-by-n matrix is created and then destroyed with the second form and this poses memory issues with large sparse matrices..
```
```
Yes this is a bug, and it has already been fixed in the CVS. With the current CVS I get
```
octave:4> a = speye(3)
a =

Compressed Column Sparse (rows = 3, cols = 3, nnz = 3)

(1, 1) -> 1
(2, 2) -> 1
(3, 3) -> 1

octave:5> a(:,[3,2,1])
ans =

Compressed Column Sparse (rows = 3, cols = 3, nnz = 3)

(3, 1) -> 1
(2, 2) -> 1
(1, 3) -> 1

Cheers
David

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