Help needed vectorizing layer-wise 3d logical indexing problem.

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MyZ Zhang
MyZ Zhang 2015-12-10
编辑： Mohammad Abouali 2015-12-10
Hi folks,
I currently have a 3D logical array and a 2D matrix and I would like to logically index the 2D matrix using each layer of the logical array. I was wondering whether there was a faster, possibly more vectorized way that avoids a for loop.
eg.
A is p x q
B is p x q x r
C is cell(1,r)
for i = 1:r
C{i} = A(B(:,:,i));
end
Is there a one liner that can do this. My motivation is that I may want to parallelize this in the future.

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Mohammad Abouali
Mohammad Abouali 2015-12-10
编辑：Mohammad Abouali 2015-12-10
% Creating Sample A and B matrix
A=rand(3,4);
B= (rand(3,4,5))>0.5;
% one liner equivalent to your code.
C=mat2cell(A(mod(find(B)-1,numel(A))+1), ...
sum(reshape(B,[],size(B,3))))
You have to check though to see if it helps. Sometimes, looping is OK.

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