How to symmetrize a matrix

Hey I want to write a code that will symmerize a non-symetric matrix by adding zeros here is code I tried writing :

   [ny,nx]=size(M);                       % current Matrix's dimensions     
   if nx~=ny                              % Comparing the dimensions
       if nx>ny                           % 
               ny=nx;                     % 
       elseif  ny>nx                      %
               nx=ny;                     % 
       end                                % 
       Z=zeros(ny,nx);                    % Creating Zero Matrix
       M=Z+M;                             % Adding zeros
       [nx,ny]=size(M);                   % current Matrix's dimentions
   end

this doesn't work because of Z and M are not the same size ... any ideas ?

Answer 1

[Andrei Bobrov]

[ny,nx]=size(M);
if ny~=nx
    m = max(ny,nx);
    M(m,m)=0;
end

[Walter Roberson]

This will not work properly if the matrix is already square, as it will overwrite the bottom-right corner with 0.

[Andrei Bobrov]

Hi Walter! You're right.

Answer 2

[the cyclist]

Andrei's method is probably the most elegant. Here is another method:

[ny,nx]=size(M);
Z = zeros(max(ny,nx));
Z(1:ny,1:nx) = M;

Be careful using the word "symmetrize" for this procedure. That term has a specific meaning in matrix algebra.