MEAN SQUARED ERROR on sectional images

I am interested in computing the mean squared error (MSE) for a section of the image; however, I get an error. Can someone assist me with it?

>> MSE=reshape(mean(mean((double(M1(192:318,1:900)) - double(M2(192:318,1:900))).^2,2),1),[1,3]);

Error: To RESHAPE the number of elements must not change.

[Image Analyst]

mean mean is one number. You're trying to shape it into a 1 by 3 array. By the way, how about going back and accepting some answers to your prior questions?

Answer 1

[Image Analyst]

Why not just say

squaredDifference = (double(M1(192:318,1:900)) - double(M2(192:318,1:900))) .^ 2
MSE = mean2(squaredDifference);