What would I need to make 'i' allow all matrices?

clc,clear

prompt = 'Give a matrix of 4x4: ';

x = input(prompt);

for i=1:16

      if x(i)<=0

         disp('Error one of the numbers put in was either a zero or negative, Fix it and start over.')

      if i~=1:16

         disp('The matrix is not a 4x4 please start again and fix the error.')
      end

      end
  end

disp(x)

Cause at the moment Im only allowed to do 4x4 or 4x5 or 4x6 i cant do 3x3 or 4x3 etc...

[John D'Errico]

Please don't post the same question again just to make a minor edit to the first one.

Answer 1

[MHN]

prompt = 'Give a matrix of 4x4: ';
x = input(prompt);
[m,n] = size(x);
 if m~=4 | n~= 4
   disp('The matrix is not a 4x4 please start again and fix the error.')
 else
    for i=1:16
    if x(i)<=0
       disp('Error one of the numbers put in was either a zero or negative, Fix it and start over.')
    end
end
end
disp(x)

Answer 2

[MHN]

prompt = 'Give a matrix of 4x4: ';
flag = 0;
while flag ==0
    x = input(prompt);
    [m,n] = size(x);
    if m==4 && n==4
        flag = 1;
    else
        disp('The matrix is not a 4x4 please start again and fix the error.')
    end
    if ~isempty(find(x<=0,1))
        disp('Error one of the numbers put in was either a zero or negative, Fix it and start over.')
        flag = 0;
    end
end