Re: Building a multidimensional block diagonal matrix avoiding loops

[PetrSt]

Try this:

clear all

A = rand([3,3,3])
[l,m,n] = size(A);

% Block diagonal in third dim
a=l; b=m*n; c=n;
B = zeros([a,b,c]);

ida = repmat((1:a)',m*n,1);
idb = reshape(repmat((1:b),l,1),l*m*n,1);
idc = reshape(repmat((1:c),l*m,1),l*m*n,1);

idx = sub2ind([a,b,c],ida,idb,idc);

B(idx) = A(:)

% Block diagonal in all dims
a=l*n; b=m*n; c=n;
B = zeros([a,b,c]);

ida = reshape(rotdim(reshape(repmat((1:a)',1,m),l,m,n),1,[2,3]),l*m*n,1);
idb = reshape(repmat((1:b),l,1),l*m*n,1);
idc = reshape(repmat((1:c),l*m,1),l*m*n,1);

idx = sub2ind([a,b,c],ida,idb,idc);

B(idx) = A(:)




--
View this message in context: 
http://octave.1599824.n4.nabble.com/Building-a-multidimensional-block-diagonal-matrix-avoiding-loops-tp4651767p4651919.html
Sent from the Octave - General mailing list archive at Nabble.com.