title: Matlab: Chi-squared fit (chi2gof) to test if data is exponentially distributed
body: <p>I guess this is a simple question, but I can't sort it out. I have a vector, the first elements of which look like:</p>
  
  <pre><code>V = [31 52 38 29 29 34 29 24 25 25 32 28 24 28 29 ...];
  </code></pre>
  
  <p>and I want to perform a <code>chi2gof</code> test in Matlab to test if <code>V</code> is exponentially distributed. I did:</p>
  
  <pre><code>[h,p] = chi2gof(V,'cdf',@expcdf);
  </code></pre>
  
  <p>but I get a warning message saying:</p>
  
  <pre><code>Warning: After pooling, some bins still have low expected counts.
  The chi-square approximation may not be accurate
  </code></pre>
  
  <p>Have I defined the <code>chi2gof</code> call incorrectly?</p>