how do I select every single element of matrix except middle

Say for example I have a 3 by 3 matrix

[1,2,3;4,5,6;7,8,9]

How do I select every element of the matrix except for the middle element?

[David Young]

What do you mean by "select"? In other words, what operation are you going to carry out on the non-central elements?

[Vaultec]

Well any operation really, For example if multiply by 2 -1. Basically I want to be able to alter every single element except the central element.

Answer 1

[Niels]

If I understand you correctly, you could do something like this:

A(A~=A(ceil(numel(A)/2)))

or

setdiff(A,A(ceil(numel(A)/2)))

Assuming you always have an odd number of elements these approaches should work.

Considering your edit, you could do it like this:

B = A([1:ceil(numel(A)/2)-1, ceil(numel(A)/2)+1:end]) * whatever;

Or, keeping it within A;

A([1:ceil(numel(A)/2)-1, ceil(numel(A)/2)+1:end]) = ...
           A([1:ceil(numel(A)/2)-1, ceil(numel(A)/2)+1:end]) * whatever;

[Vaultec]

Sorry that wasnt what I was looking for. Is there anything similar to A(1:3,1:3) and someway to remove the middle element or set it to 0 as I simply want to do operations on the remaining 8 elements

[Niels]

Check the edit I did just 1 minute after you replied again. :)