title: How do I preserve transparency in ggplot2?
body: <p>I love the plots that ggplot generates. However, it is still somewhat cumbersome to get publication quality plots directly. I usually have to do some post processing in Illustrator (i.e. changing fonts, numbering figures etc). While I could save as tiff or png, eps is best for manipulating figures in Illustrator (I can ungroup objects, move the legend/text etc).</p>
  
  <p>When I save a ggplot object with some transparency (either in points or a smoother) I get this error:</p>
  
  <pre><code>Warning message:
  In grid.Call.graphics("L_points", x$x, x$y, x$pch, x$size) :
    semi-transparency is not supported on this device: reported only once per page
  </code></pre>
  
  <p>Is there a workaround? </p>