Matrix operation in Matlab

It would be more helpfull if you show the code relevant for your question.

In general when using Matlab you often doesnt have to loop e.g. through an image (pixel by pixel) but can make use of Matlabs ability to process a matrice "as a whole". The term for this technique is called Vectorization. See here how it may be done: http://www.mathworks.de/de/help/matlab/matlab_prog/vectorization.html