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sub2ind Get values of 3D matrix using an index array?

Asked by Penny Less on 10 Sep 2019
Latest activity Commented on by Penny Less on 11 Sep 2019
Hi all,
I have a 800x900x7 matrix (matrix M) and a 800x900 2D array (matrix A) whose elements are the indexes i want to obtain from each row and column in matrix M (so each element in array A is a number from 1 to 7).
The final result should be an 800x900 matrix (matrix F) containing the elements in matrix M which matrix A specifies.
Without using a for loop, how am I able to do this? I'm thinking sub2ind, but any help would be greatly appreciated!
Many thanks

  1 Comment

You mean A matrix are indices? Could you illustrate with 2by2 A matrix and a 2by2by2 M matrix?

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1 Answer

Answer by Andrei Bobrov
on 10 Sep 2019
 Accepted Answer

[m,n,k] = size(M);
[q,w] = ndgrid(1:m,1:n);
out = M(sub2ind([m,n,k],q,w,A));

  1 Comment

Works perfectly, thank you!

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