MATLAB: Trouble with vectorization of the following code containing for loops and logical indexing

bsxfunfor loopslogical indexingMATLABvectorization

I have been working on vectorizing my code mostly using bsxfun, but I came across a scenario that I can't quite crack. Here is a small sample of problem. I would like to remove the for loops in this code, but I am having a hard time with the tempEA line.
Index = [2; 3; 4;];
dTime = [25; 26; 27; 28; 25; 26; 27; 28; 27; 28];
dIndex = [3; 3; 3; 2; 1; 3; 2; 4; 4; 2];
aTime = [30; 38; 34; 39; 30; 38; 34; 39; 34; 39];
aIndex = [4; 2; 5; 4; 5; 4; 4; 2; 2; 4];
EA = zeros(numel(Index));
for i = 1:numel(Index)
for j = 1:numel(Index)
tempEA = aTime(Index(i) == dIndex(:,1) & Index(j) == aIndex(:,1));
if i == j
elseif tempEA > 0
EA(i,j) = min(tempEA);
else
EA(i,j) = 50;
end
end
end
The answer should look like this:
EA =
0 50 34
38 0 30
34 50 0
Thanks for help in advance.

Best Answer

  • ai = bsxfun(@eq,Index(:)',reshape(aIndex,1,1,[]));
    di = bsxfun(@eq,Index(:),reshape(dIndex,1,1,[]));
    ii = bsxfun(@and,ai,di);
    A = bsxfun(@times,ii,reshape(aTime,1,1,[]));
    A(A==0)=inf;
    EA = min(A,[],3);
    EA(1:size(EA,1)+1:end) = 0;
    EA(isinf(EA)) = 50;