title: Not able to install xkcd fonts
body: <p>I was trying the xkcd font as per the instructions given in the vignette: <code>vignette("xkcd-intro")</code></p>
  
  <p>However get an error on the following step:</p>
  
  <pre><code>&gt; system("cp xkcd.tff -t ~/.fonts")
  cp: xkcd.tff: No such file or directory
  cp: -t: No such file or directory
  </code></pre>
  
  <p>What to do??</p>