title: Very strange graphs with ggplot2 geom_violin
body: <p>I could only reliably reconstruct this problem with a pretty large data set, so I pasted the entire code <a href="http://pastebin.ca/2465250" rel="nofollow noreferrer">to a pastebin</a>
  Here is the code without the data part:</p>
  
  <pre><code>    # read tmp from the pastebin  
  
  library(ggplot2)
  plt &lt;- ggplot(tmp, aes(region, score))
  plt1 &lt;- plt + geom_violin(aes(region, score), scale='width', trim=F)  + ylim(0, 1) + ggtitle('with ylim')
  plt2 &lt;- plt + geom_violin(aes(region, score), scale='width', trim=F)  + ggtitle('without ylim')
  </code></pre>
  
  <p>Setting y limits for this plot results in pretty ugly "violins":</p>
  
  <p><img src="https://i.stack.imgur.com/BR5mF.png" alt="enter image description here"></p>
  
  <p><img src="https://i.stack.imgur.com/INFVe.png" alt="enter image description here"></p>
  
  <p>What is this, why does this happen and how to avoid this ugly problem? </p>
  
  <p>BTW, setting <code>trim=T</code> solves the problem.</p>