Question

I know this is a simple question but difficult to formulate in one sentence to google the answer.So, I have a 3d matrix with size 2x2x3 like this

A(:,:,1) =[1     1;  1    1];
A(:,:,2) =[2     2; 2     2];
A(:,:,3) =[4     4; 4     4];

and matrix B with size 2×2

B = [ 1 2; 2 3];

What i need is to chose from each third dimension in A just one number using matrix B:

for i=1:2,
  for j=1:2,
    C(i,j) = A(i,j,B(i,j));
  end
end

How to that in one line without a loop?

Answer 1

Not really a single line, but without a loop:

[I J] = ind2sub (size(B), 1:numel(B));
linInd = sub2ind (size (A), I, J, B(:)');
C = reshape (A(linInd), size(B));