How to vectorize this code to eliminate nested For loops

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.

[Rik]

Is segMat a function or an array? The second set of loops could be replaced with a call to arrayfun, but this is not always a speed improvement.

[Jae Min Lee]

segMat is an image array.

Answer 1

[Walter Roberson]

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);

[Jae Min Lee]

Thank you very much.