# MATLAB: Matrix neighbours chaning with iterations

changeiterationmatrixneighbour

Imagine I have matrix A=ones(5). I want to change center of the matrix to 17, A(3,3)=17; In next iteration I want to change all points that are next to this 20 to 5. i will have:
1  1  1  1  11  5  5  5  11  5 17  5  11  5  5  5  11  1  1  1  1
In next step i want to change all ones to 10. And so on…
10 10 10 10  1010  5  5  5  1010  5 17  5  1010  5  5  5  1010 10 10 10  10
Any idea how to do this to large matrix? How to adress only the neighbours but not the points "inside"?

• [M,N]=size(A);center=size(A)/2+.5;   [I,J]=ndgrid((1:M)-center(1), (1:N)-center(2));   A(:) = 20-5*round(max(abs(I),abs(J)))