title: arrow() in ggplot2 no longer supported
body: <p>Installed R 2.15.2 on a new machine and ggplot2.  The grid package is no longer supported in this latest version of R, but ggplot2 uses grid for the <code>arrow()</code> function, as in these examples.</p>
  
  <p><a href="http://docs.ggplot2.org/current/geom_segment.html">http://docs.ggplot2.org/current/geom_segment.html</a></p>
  
  <p>Haven't been able to find a workaround.  Any suggestions?</p>