Summation and array indexes

2014 10 13
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更新时间：2014 10 14
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I am trying to write a function for an optimisation routine that requires the (total) summation of a matrix divided element by element by a second matrix, where the second matrix has a third dimension returning a vector the size of that third dimension.
i.e. something along the lines of a(1:n) = sum(sum(A./B(:,:,1:n))
which doesn't work. Any ideas?
Thanks

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Adam
Adam 2014-10-13
Can you give a simple example of inputs A and B?
Dale
Dale 2014-10-14
编辑：Dale 2014-10-14
Hi Adam
A is a m x m matrix, and B is a m x m x n matrix.
I am aware I could do this with a loop (below), was just seeing if it is possible with direct indexing...
for i = 1:n
a(i) = sum(sum(A./B(:,:,i)))
end

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Guillaume
Guillaume 2014-10-14

1 个投票

Use bsxfun to perform your division
a = squeeze(sum(sum(bsxfun(@rdivide, A, B))));

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Adam
Adam 2014-10-14

1 个投票

c = bsxfun( @rdivide, A, B );
a = squeeze( sum( sum( c ) ) );
should give the answer you want. Obviously you could do it in one line if you prefer.

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