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annotate toolboxes/FullBNT-1.0.7/KPMtools/max_mult.m @ 0:e9a9cd732c1e tip

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first hg version after svn
author wolffd
date Tue, 10 Feb 2015 15:05:51 +0000
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wolffd@0 1 function y=max_mult(A,x)
wolffd@0 2 % MAX_MULT Like matrix multiplication, but sum gets replaced by max
wolffd@0 3 % function y=max_mult(A,x) y(i) = max_j A(i,j) x(j)
wolffd@0 4
wolffd@0 5 %X=ones(size(A,1),1) * x(:)'; % X(j,i) = x(i)
wolffd@0 6 %y=max(A.*X, [], 2);
wolffd@0 7
wolffd@0 8 % This is faster
wolffd@0 9 if size(x,2)==1
wolffd@0 10 X=x*ones(1,size(A,1)); % X(i,j) = x(i)
wolffd@0 11 y=max(A'.*X)';
wolffd@0 12 else
wolffd@0 13 %this works for arbitrarily sized A and x (but is ugly, and slower than above)
wolffd@0 14 X=repmat(x, [1 1 size(A,1)]);
wolffd@0 15 B=repmat(A, [1 1 size(x,2)]);
wolffd@0 16 C=permute(B,[2 3 1]);
wolffd@0 17 y=permute(max(C.*X),[3 2 1]);
wolffd@0 18 % this is even slower, as is using squeeze instead of permute
wolffd@0 19 % Y=permute(X, [3 1 2]);
wolffd@0 20 % y=permute(max(Y.*B, [], 2), [1 3 2]);
wolffd@0 21 end