How to replace an element with average of surrounding elements excluding that particular element?

This is similar to

A=[1 2 3; 4 5 6; 7 8 9];
conv2(A, ones(3), 'same') ./ conv2(ones(size(A)), ones(3), 'same');
ans =

    3.0000    3.5000    4.0000
    4.5000    5.0000    5.5000
    6.0000    6.5000    7.0000

But this includes the central elements also. I want to exclude those elements and replace the elements by average of surrounding elements only. e.g. 1 should be replaced by 3.67, not 3.

Answer 1

[Walter Roberson]

If not for boundary conditions, you could use

[1 1 1; 1 0 1; 1 1 1]/8

For boundary conditions, consider what happens if you conv2(ones(size(A)), ones(3),'same')

[Shaunak Chatterjee]

I think this may work.

window=3;
convwindow=ones(window);
convwindow(round(window/2),round(window/2))=0;
conv2(A, convwindow, 'same') ./ conv2(ones(size(A)), convwindow, 'same');

This is working for my matrix.