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Adding elements of matrix according to criteria

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V
V 2015-3-8
编辑： Matt J 2015-3-9
Hi there,
I have a quick question which should be trivial to solve but I cannot figure out how to solve it.
I have 2 matrices:
  • Matrix A with dimensions (2x40x2x1000)
  • Matrix B with dimensions (2x40x2)
I want to add matrix A elements along the 4th dimension if the element is above the one on matrix B.
So if elements (1,1,1,:) of matrix A are bigger than element (1,1,1) of matrix B, I want to add them up. If elements (2,1,1,:) of matrix A are bigger than element (2,1,1) of matrix B, I want to add them up. etc
What is the easiest way to do it?

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回答（2 个）

Matt J
Matt J 2015-3-9
编辑：Matt J 2015-3-9
mask=bsxfun(@gt,A,B);
result=sum(A.*mask,4);
Jan
Jan 2015-3-8
The term "add them up" is not clear. A small example would be nice. I guess it could mean something like this:
S = zeros(size(B));
for k = 1:1000
Ak = A(:, :, :, k);
M = Ak > B;
S(M) = S(M) + Ak(M);
end
Or:
S = zeros(size(B));
for k = 1:1000
Ak = A(:, :, :, k);
S = S + Ak .* (Ak > B);
end

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