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Re: manipulating sparse matrices

From: Andy Adler
Subject: Re: manipulating sparse matrices
Date: Fri, 14 Oct 2005 21:26:12 -0400 (EDT)

On Fri, 14 Oct 2005, Mike Miller wrote:

> I'm using Octave 2.1.71 on Linux with Octave-Forge 2005.06.13.
> I have two questions about sparse matrices...
> If I do this...
> a = speye(1000);
> a(1,1) = 2;
> ...the resulting 'a' matrix is no longer of class "sparse" and it takes up
> 8 MB of RAM.  That's not good for me.  Is there a way to reassign an
> element of a sparse matrix without changing its class?  I believe this
> just works in 2.9, but is there a way to do it in 2.1.71?

That is correct. The sparse code in octave-forge does not support
assignment. David Bateman has stated that his need for this feature
was the primary motivator for writing the new sparse code in 2.9.x.

Andy Adler <address@hidden> 1(613)562-5800x6218

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