title: Right (or left) side trimmed mean
body: <p>Using:</p>
  
  <pre><code>mean (x, trim=0.05)
  </code></pre>
  
  <p>Removes 2.5% from each side of the distribution, which is fine for symmetrical two-tailed data. But if I have one tailed or highly asymmetric data I would like to be able to remove just one side of the distribution. Is there a function for this or do I have write myself a new one? If so, how?</p>