how to replace a matrix element by the avearage of its surrounding elements

   1 2 3
A= 4 5 6
   7 8 9
is a matrix
resultant matrix
   11/3 19/5 13/3 
B= 23/5 40/8 27/5
   17/3 31/5 19/3

Answer 1

[Henric Rydén]

    A=[ ... 
  1 2 3 ; ...
  4 5 6 ; ...
  7 8 9];

    kernel = [ ...
  1 1 1; ...
  1 0 1 ; ...
  1 1 1];

neighbors = imfilter(ones(size(A)),ones(size(A)))-1;

result = imfilter(A,kernel) ./ neighbors;