Matrix-vector boolean comparison

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Greg
Greg 2011-10-11
I might be having a brain fart, but if I'm not...
I have a matrix M (mxn) and a vector V (mx1). On each row of M, I want to see how many elements are greater than the element on the corresponding row of V. That is, I want R, where
for i=1:m;
R(i)=length(find( M(i,:) > V(i)));
end
My question is - can I do this without a loop? Is there a one line operation for this? I know the loop in the example is trivial, but I'm trying to optimize code that takes hours to run and where I run through the loop many many times.

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Sean de Wolski
Sean de Wolski 2011-10-11
Sure:
R = sum(bsxfun(@gt,M,V),2)
Also note, just preallocating R would save you a lot of time for large m.
R = zeros(m,1);
for ii =...
R(ii) = ...
end
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Greg
Greg 2011-10-11
Awesome. Preallocating was done, smarter things weren't. Thanks!

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