matrix indexing without loop

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mcdull hall
mcdull hall on 2 Aug 2018
Commented: mcdull hall on 2 Aug 2018
Hello,
Suppose I have two matrices, A and B:
A = [2 3 1 4;
1 4 1 3];
B = [1 2 3 4;
4 3 2 1];
Now I get the max indices for the matrix A:
[~,ind] = max(A,[],2);
I want to obtain the corresponding values of matrix B with ind:
for ii = 1:2
v(ii) = B(ii,ind(ii));
end
How to get the values of B without a for loop?

Accepted Answer

Walter Roberson
Walter Roberson on 2 Aug 2018
v = B(sub2ind(size(B), 1:size(B,1), ind))
  1 Comment
mcdull hall
mcdull hall on 2 Aug 2018
By the way, it should be:
v = B(sub2ind(size(B), (1:size(B,1))', ind))
Thanks.

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