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How I can vectorize the next code?
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Hello. M is a matrix and v and w are vectors of the same length containing some indices of M. I want to vectorize the following code (without using loops)
for i=1:length(v);
M(v(i),w(i)) = 1;
end
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Answers (3)
Azzi Abdelmalek
on 1 Oct 2012
Edited: Azzi Abdelmalek
on 1 Oct 2012
M=magic(5); % example
v=1:2;
w=3:4
idx=sub2ind(size(M),v,w)
M(idx)=1
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Image Analyst
on 1 Oct 2012
You simply do
M(v, w) = 1;
Here's proof:
M = magic(10)
v = randi(10, 5,1)
w = randi(10, 5,1)
M(v,w) = 1
2 Comments
Image Analyst
on 1 Oct 2012
Edited: Image Analyst
on 1 Oct 2012
Ah, you're right, that won't work (though it seems like it would). Use Azzi's code then.
Andrei Bobrov
on 1 Oct 2012
Edited: Andrei Bobrov
on 1 Oct 2012
M = randi([100,300],10);
v = randi(10,7,1);
w = randi(10,7,1);
M(v + size(M,1)*(w-1)) = 1
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