Re: Building a multidimensional block diagonal matrix avoiding loops

[Jose]

Hello.

On 04/12/2013 09:47 PM, c. wrote:
> On 12 Apr 2013, at 20:43, Jose <address@hidden> wrote:
>
> > Hello.
> >
> > I need to create a multidimensional block diagonal matrix from another 
> > multidimensional matrix. Let me put a simplified example.
> >
> > I have A
> > A(:,:,1)=[1 2;3 4];
> > A(:,:,2)=[5 6;7 8];
> >
> > from which I want to create B
> > B(:,:,1)=[1 2 0 0;3 4 0 0];
> > B(:,:,2)=[0 0 5 6;0 0 7 8];
> >
> > so the expansion occurs in diagonal blocks in the second dimension.
> >
> > If I had the problem with a 2D matrix, I could combine mat2cell and blkdiag to 
> > create the new expanded matrix. But having a multidimensional matrix I cannot 
> > see a way to avoid a loop, such as for example:
> >
> > [l,m,n]=size(A);
> > for k=1:n
> >   B(:,:,k)=[zeros(l,m*(k-1)) A(:,:,k) zeros(l,m*(n-k))];
> > endfor
> >
> > Anybody has any idea about how to make this avoiding the loop?
> >
> > BR
> > Jose
>
> I think the function "kron" could be of help with your problem.

Thanks for the suggestion, but the "kron" function does not seem to work 
with multidimensional matrices. So I still don't see how I could avoid 
the loop.

BR
J.