selecting elements in matrix based on a vector

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Champ
Champ 2012-2-8
编辑： dpb 2013-10-5
suppose I have a matrix [1,2,3,4; 5,6,7,8; 1,2,3,4; 5,6,7,8] and a select vector that will pick an element from each row of the matrix [1;2;2;3] (so it will pick first column element from the first row, second column element from the second row, second column element from the third row and third column element from the fourth row)
How do I code so that the vector "pick" elements from the matrix and the result becomes [1;6;2;7]

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Sean de Wolski
Sean de Wolski 2012-2-8
A(sub2ind(size(A),(1:numel(idx))',idx(:)))
where A is your matrix above and idx is your vector.
Or you could go this route:
diag(A(1:numel(idx),idx))

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