how change elements around the special element in matrix

Hello please guide me.

A is

    A=zeros(100,100)

i a j is selected randomly for example i=9 and j=8. I want to change element of matrix A to 1 on the basis of i and j. In fact elements that are around the element(i=9,j=8) should be changed to 1. my picture shows that. yellow cell is (i=9,j=8) and orange cells should be changed. each time i and j may be changed and this will change everything. Thank you

Answer 1

[Image Analyst]

Try this:

A(i-3:i+3, j-3:j+3) = 1; % Or whatever value you want.

If you want to change just the surrounding values and not the i,j value, then save it and restore it:

savedValue = A(i,j);
A(i-3:i+3, j-3:j+3) = 1; % Or whatever value you want.
A(i,j) = savedValue;

[fatema saba]

Thank you very much

[fatema saba]

But if i and j point to element that is located on the border of matrix A, this makes some problem.

[fatema saba]

Thank you. I got it