When does the error Matrix dimension exceeds comes?

The formula (x-d:x+d,y-d:y+d) is used to find a square region inside a circular feature.In a 512X512 image when the values of x,y and d are the following x=501 y=237 d=4 it displays matrix dimension exceeds. What is the problem in it?

Answer 1

[Amit]

for whichever matrix you are applying (x-d:x+d,y-d:y+d), can you first do a

whos A

to check if the size of the array is 512x512. Because otherwise it should work.