Summation and array indexes

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

[Adam]

Can you give a simple example of inputs A and B?

[Dale]

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

Answer 1

[Guillaume]

Use bsxfun to perform your division

a = squeeze(sum(sum(bsxfun(@rdivide, A, B))));

[Dale]

Perfect, thanks!

Answer 2

[Adam]

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.

[Adam]

Ah, too late! :)

Answer 3

[Roger Stafford]

   sum(A(:))./sum(sum(B,1),2)