help changing the counter when converting a for loop to while loop

M=input('Enter your proposed magic square in a sigle input statement (4x4 matrix) []: ');

[r,c]=size(M);

for i=1:1:r
  for j=1:1:c
      a=sum(M(i,:));
      b=sum(M(:,i));                      % I need help converting this for 
      x(i)=(M(i,i));                        loop into a while loop
      d(i)=(M(i,5-i));                     
      f=sum(x);                           % I'm not sure what to set my 
      g=sum(d);                             variables as
  end
end

[Walter Roberson]

You never use "j" in your "for j" loop, and you overwrite "f" and "g" during each iteration of the "for j" loop. Please repair your code first.