MATLAB: Retrieve value from specific location of matrix

matrixsub2indvalue

Hi suppose I have a matrix as follows:
m =
     1     1
     1     3
     1     5
     2     2
     2     4
     3     1
     3     3
     3     5
each row of m is the row,column index respectively.
And I have another matrix I.
I need to find the values of I of location m. How can I do that?
Is there anybody to help me? Thanks

Best Answer

use sub2ind to create from coordinates an index that points to the position.
m = [1     1
     1     3
     1     5
     2     2
     2     4
     3     1
     3     3
     3     5]
I = rand(5);
sub2ind(size(I),m(:,1),m(:,2))
To skip the overhead you can apply the engine of sub2ind directly (2d adaptation):
(m(:,2)-1)*size(I,1) + m(:,1)
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