If you want to put the four smaller arrays into separate variables, you can do it like this (assuming the sizes are even as stated):
topLeft = A(1:end/2, 1:end/2);
topRight = A(1:end/2, end/2+1:end);
bottomLeft = A(end/2+1:end, 1:end/2);
bottomRight = A(end/2+1:end, end/2+1:end);
Then process each small array in any way you like.
But perhaps you want to do this in a loop, processing each quadrant in turn? If so, you can probably work out what to do from the code above, but it it's still a problem please say.
