Issue with mean function

Hi,

I am wanting to make each element in an array (excluding the first and last rows & columns, i.e. the elements on the edge) the average of that element and the 8 surrounding elements using the mean() function. The mean function is currently returning a 1x125 matrix where each element is the average of the elements in each corresponding column in the original 125x125 matrix. Is there a way I can make the mean function return a 125x125 matrix (the same size as the original matrix to be averaged)? It's for a uni assessment and we're supposed to use the mean function.

Cheers, Bruce

[Daniel Shub]

Although by a different user, this is a duplicate of http://www.mathworks.com/matlabcentral/answers/38766-averaging-matrix-and-store-it-in-a-new-matrix

Answer 1

[Titus Edelhofer]

You will need to do exactly what you are describing: taking for each element the mean of the surrounding elements. What you did was to compute the mean of the entire matrix ...

Titus

Answer 2

[Sean de Wolski]

Sure, you could do this with mean() and a couple of for-loops but conv2() is way cooler:

xm3x3 = conv2(x,ones(3)*mean([0 1/9 2/9]),'same');

[Image Analyst]

Of course he has conflicting requirements. "(excluding the first and last rows & columns, i.e. the elements on the edge) " means that he want the 'valid' option of conv2(), while "(the same size as the original matrix..." means that he wants the 'same' option of conv2().

[Sean de Wolski]

I saw that. When in doubt, go same, it's easier to extract than create.