Calculating mean of matrix elements

Hey guys,

I need a bit of help regarding calculating the mean of elements in a matrix. I want to calculate the mean of each value and the eight values surrounding it (excluding elements in the first / last rows and first/ last columns), then display the mean values in a new matrix, with the first / last rows and columns from the original matrix in place. Here is some code that I have put together but cannot seem to get to work:

x = 300x300 matrix

 for i = x(2:299, 2:299)

    x = [rows, cols];

    for rows = 0:255

        for cols = 0:255

    q = [[rows, cols], [rows-1, cols-1], [rows-1, cols], [rows-1, cols+1], [rows, cols+1], [rows+1, cols-1], [rows+1, cols], [rows+1, cols+1]];

    m = mean(q);

        end
    end
end

 n = [m + x(1, 1:300) + x(300, 1:300) + x(1:300, 1) + x(1:300, 300)];

[Andrei Bobrov]

http://www.mathworks.com/matlabcentral/answers/7567-accessing-surrounding-elements-in-an-array

[J.C.]

I looked at that page before asking this question and tried the code displayed, but couldn't get it to run properly / produce the correct output. Could you please explain exactly what the code is doing? Thanks

Answer 1

[Sean de Wolski]

x = magic(300); %example matrix
x2 = conv2(x,ones(3)/9,'valid'); %windowed mean of 3x3 grid
x(2:end-1,2:end-1) = x2; %insert