title: Export plot as pdf with a utf8 character
body: <p>The utf8 character in the label does not appear when I save the plot in pdf format. It does not appear when I use the "Export" button in RStudio, and it does not appear when I include this code in a Sweave document with pdf graphics output. My problem is to get the correct pdf output with Sweave (not knitr). 
  (If I don't find a solution, I will generate it with <code>tikzDevice</code>)</p>
  
  <pre><code>ylab &lt;- expression(paste("", bar(italic("\u2113")), "(",phi[0], "|", italic(list(x,y)), ")"))
  plot(0,0, ylab=ylab)
  </code></pre>