Re: Gallery (or circulant matrices)

[Jeffrey]

Thanks, Markus. I'm afraid this didn't work. You can't subtract (1:length(v)) from (1:length(v))'. Did you mean to repmat them, somehow?

On Fri, Jun 7, 2013 at 9:13 PM, Markus Appel [via Octave] <[hidden email]> wrote:

On 06/08/2013 02:26 AM, Jeffrey wrote:

> Converting from Matlab, the "gallery" command to create circulant
> matrices is not implemented. Is there an Octave equivalent to
>
> K=gallery('circul',[4 -1 zeros(1,N-3) -1]);
>
> How does one find octave equivalents to Matlab statements? Thanks.

I can't answer the general question of how to find equivalents, but in
the special case of this matrix (and if i understood the 'circul'
gallery function right) you should be able to substitute

K=gallery('circul',v)

by

K = v( 1 + mod( (1:length(v))' - (1:length(v)), length(v)) )

The _expression_ is basically creating an index matrix with shifted
columns and picking the elements out of your input vector v in the right
order.

Hope it helps,
Markus
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