Logical Indexing: Using a 1x18 array to build a 200*18 matrix

Hello,

Failmatrix is a 200x18 binary matrix. Costmatrix is a 1x18 array of cost integers.

I am trying to create a 200x1 matrix where each row is the combined total of the costmatrix values where failmatrix ==1. If that makes sense.

The following does not produce an error message, however rebuildcost stays at zero.

for i =1:length(failmatrix(:,1))
rebuildcost = costmatrix(failmatrix(i,:)==1); 
rebuildcost = sum(rebuildcost);
end

Can anyone advise? Thank you.

Answer 1

[Guillaume]

Simply:

rebuildcost = sum(failmatrix .* costmatrix, 2);  

[Stephen]

Wow, very simple, I need to keep practicing haha

Thank you again Guillaume.