title: How can I use numpy.correlate to do autocorrelation?
body: <p>I need to do auto-correlation of a set of numbers, which as I understand it is just the correlation of the set with itself. </p>
  
  <p>I've tried it using numpy's correlate function, but I don't believe the result, as it almost always gives a vector where the first number is <em>not</em> the largest, as it ought to be.</p>
  
  <p>So, this question is really two questions:</p>
  
  <ol>
  <li>What exactly is <a href="https://docs.scipy.org/doc/numpy/reference/generated/numpy.correlate.html" rel="noreferrer"><code>numpy.correlate</code></a> doing?</li>
  <li>How can I use it (or something else) to do auto-correlation?</li>
  </ol>