how can i vectorize this loop?

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Miguel Reina
Miguel Reina 2018-1-21
回答： Matt J 2018-1-22
K=100;
a=zeros(K,1);
for u = 0:K-1
for b = 0:K-1
a(u+1) = a(u+1) + s(b+1)*exp((-2j*pi*u*b/K));
end
end

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采纳的回答

Matt J
Matt J 2018-1-21
a=fft(s);

更多回答（2 个）

Image Analyst
Image Analyst 2018-1-21
Well you could try meshgrid() but I think it might make it a little more confusing to understand what it's doing. With only 100x100 array to fill, a double for loop will be very fast so even if you did vectorize it, don't expect to notice any speed difference.
Matt J
Matt J 2018-1-22
A less efficient way,
z=0:K;
a=exp((-2j*pi/K)*z.'*z)*s(:);

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