title: How can I assign different symbols to different groups in a lattice plot?
body: <p>Say I have 3 groups with 3 dots each on the plot and I need a black &amp; white version where the 3 dots of the 3 groups are all displayed with different symbols.
  How should I specify the panel.superpose function?</p>
  
  <p><a href="http://www.r-bloggers.com/working-with-themes-in-lattice-graphics/" rel="nofollow">http://www.r-bloggers.com/working-with-themes-in-lattice-graphics/</a>
  http://stat.ethz.ch/R-manual/R-devel/library/lattice/html/panel.superpose.html</p>