I wan to create a 3x3 matrix and this matrix needs to contains first 3 raws and last 3 columns of other matrix which is unknown.

I wan to create a 3x3 matrix and this matrix needs to contains first 3 raws and last 3 columns of other matrix which is unknown. How can i do that ? Can you help me about it ?

Answer 1

[Mitchell Thurston]

With the original larger matrix you want the rows and columns from being "A" and the resulting 3x3 being "B",

A = B(1:3, ... % to specify first 3 rows
      end-2:end); % to specify last 3 columns

Since I'm assuming you want this to be a function, and B could be anything (including a matrix less than 3x3, it would be a good idea to have an error check.

function A = first3last3(B)
    m,n = size(B);
    if (m<3) || (n<3)
        error('Input matrix is improper size');
    end
    A = B(1:3, n-2:n);
end