title: Finding the intersection between two series in Pandas
body: <p>I have two series <code>s1</code> and <code>s2</code> in pandas and want to compute the intersection i.e. where all of the values of the series are common.</p>
  
  <p>How would I use the <code>concat</code> function to do this? I have been trying to work it out but have been unable to (I don't want to compute the intersection on the indices of <code>s1</code> and <code>s2</code>, but on the values).</p>