title: tutorial code for octave gives me weird error
body: <pre><code>% create GMM
  mu = [0; 5];
  sigma = cat(3, 1, 2);
  p = [0.5; 0.5];
  gmm = gmdistribution(mu, sigma, p);
  
  % view PDF
  ezplot(@(x) pdf(gmm,x));
  </code></pre>
  <p>I'm trying to run this small tutorial code since i'm new to octave</p>
  <p>but everytime I run this code it gives me error</p>
  <pre><code>error: gmdistribution.pdf: X has 500 columns instead of 1
  </code></pre>
  <p>what does this error mean?</p>
  <p>How do I fix it?</p>