title: xcorr (for autocorrelation) with NaN values
body: <p>I'd like to autocorrelate some data but it has some missing values, is there a quick way to do this in matlab? xcorr returns an array of NaN if any of the input is NaN.</p>
  
  <p>e.g.</p>
  
  <pre><code>data = [1 2 3 4 NaN 2 3 4 1 2 3 4];
  xc = xcorr(data, 'biased');
  </code></pre>