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.
This uses bsxfun
; no loops. It assumes you don't have NaN
's among your aTime
values.
N = numel(Index);
ii = bsxfun(@eq, dIndex.', Index); %'// selected values according to each i
jj = bsxfun(@eq, aIndex.', Index); %'// selected values according to each j
[ igrid jgrid ] = ndgrid(1:N); %// generate all combinations of i and j
match = double(ii(igrid(:),:) & jj(jgrid(:),:)); %// each row contains the matches for an (i,j) combination
match(~match) = NaN; %// these entries will not be considered when minimizing
result = min(bsxfun(@times, aTime, match.')); %'// minimize according to each row of "match"
result = reshape(result,[N N]);
result(isnan(result)) = 50; %// set NaN to 50
result(result<=0) = 50; %// set nonpositive values to 50
result(1:N+1:end) = 0; %// set diagonal to 0
The line result(result<=0) = 50;
is only necessary if your aTime
can contain nonpositive values. Can it? Or is your elseif tempEA > 0
just a way of checking that tempEA
is not empty?