Matrix manipulation

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Pedro Cavaco
Pedro Cavaco 2011-4-12
Hi,
I have a matrix A(1000,6) and i want to write 1's at certain positions say:
i = [785 58 595 389 450 956];
j = [4 6 2 3 5 1];
If I do A(i,j) = 1 it places 1's in the positions "i" of all the columns "j".
But what i want is:
A(i(1),j(1)) = 1
A(i(2),j(2)) = 1
...
A(i(end),j(end)) = 1
Does anybody knows how to do this without having to use a for loop?
  1 个评论
Teja Muppirala
Teja Muppirala 2011-4-12
Is there a compelling reason not to use a FOR loop? A loop will probably do this faster than any non-loop solution (that I can think of anyways).

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采纳的回答

Andrei Bobrov
Andrei Bobrov 2011-4-12
variant
i = [785 58 595 389 450 956];
j = [4 6 2 3 5 1];
A(sub2ind(size(A), i, j)=1;

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