How to select (and assign) values within a specific subregion of a matrix

Hello, I am struggling with a problem and I cannot find the solution anywhere, I hope someone could help me out. A is a matrix, specifically A = zeros(81,81); and A(32,32)=1. I am trying to select the values within a square-shaped region with center in A(32,32) and radius 2 (i.e. from the center to +- 2 rows and to +-2 columns, please see the example below), and assign them the value of 2. So, if this is the original matrix (here smaller for practical reasons): A = zeros(7); A(4,4) = 1 A =

     0     0     0     0     0     0     0
     0     0     0     0     0     0     0
     0     0     0     0     0     0     0
     0     0     0     1     0     0     0
     0     0     0     0     0     0     0
     0     0     0     0     0     0     0
     0     0     0     0     0     0     0

I would like this to be the result: A =

     0     0     0     0     0     0     0
     0     2     2     2     2     2     0
     0     2     2     2     2     2     0
     0     2     2     1     2     2     0
     0     2     2     2     2     2     0
     0     2     2     2     2     2     0
     0     0     0     0     0     0     0

Does anyone know how I could assign the value of 2 to the values within that region, without doing it manually for each element?

Any help would be very appreciated. Thank you in advance!

[Esha Bhargava]

The following links show examples of matrix indexing: http://www.mathworks.com/help/matlab/math/matrix-indexing.html http://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

Answer 1

[Andrei Bobrov]

use function bwdist from Image Processing Toolbox

out = (bwdist(A,'chessboard')<3)*2-A;