Re: Gallery (or circulant matrices)

[Markus Appel]

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