MATLAB: How to vectorize this code to eliminate nested For loops

for loopvectorization

Would like to know how this code be vectorized:
for y=1:rows
  for x=1:cols
      if (segMat(y,x) == 255)
          Energy(y,x) = Energy(y,x) + motionMap(y,x);            
      end
  end
for y=1:rows
  for x=1:cols
      delta(y,x) = kronDel(255, segMat(y,x));
  end
end
The kronDel function acts like the Kronecker delta.

Best Answer

Assuming that motionMap is an array and not a function,
   %no loop needed
   mask = segMat == 255;
   Energy(mask) = Energy(mask) + motionMap(mask);
After which you can have the second nested loop calling kronDel
kronDel looks more likely to be a function than an array, so it is difficult to know if we could vectorize that section.
I speculate that your kronDel function returns the first parameter if the second parameter is 0, and otherwise returns 0. If my speculation is correct, then the loops and call could be replaced by
delta = 255 .* (segMat == 0);
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