Which part of this is a non-negative integer? (factorial error) : <p>This is the script:</p>

<pre><code>n=input('Enter the number of rows: ')
PT=zeros(n);
row=1;
col=1;
while row~=n+1
  for col=1:1:n
    PT(row, col)=(factorial(row-1)/(factorial(col-1)*factorial(row-col)));
  end 
  row=row+1;
  col=1;
end
PT
</code></pre>

<p>When I run it, it says to enter the number of rows, so I enter '4'. Then it says </p>

<pre><code>error: factorial: all N must be real non-negative integers
error: called from
    factorial at line 40 column 5 
    hw6p2 at line 7 column 17 
</code></pre>

<p>I don't understand what's wrong.</p>
