title: Color countries on world map based on ISO3 codes in R using ggplot()
body: <p>I wonder whether I can color countries using <code>ggplot</code>? Using <code>rworldmap</code> this is pretty simple and adding points to lat/long values via <code>ggplot</code> is easy as well.
  <p>
  Is there a way of coloring countries based on a simple table using <code>ggplot</code> (country names in ISO3 and a number for each country?) The coloring should be based on the count.</p>
  
  <pre><code>p &lt;- ggplot(legend=FALSE) +
  
  geom_polygon(fill = "darkseagreen", data=world, aes(x=long, y=lat,group=group)) + 
   geom_path(colour = "grey40") + 
   theme(panel.background = element_rect(fill = "lightsteelblue2", colour = "grey")) +
   theme(panel.grid.major = element_line(colour = "grey90")
  ) +
   theme(panel.grid.minor = element_blank()) +
   theme(axis.text.x = element_blank(),
   axis.text.y = element_blank()) +
   theme(axis.ticks = element_blank()) +
   xlab("") + ylab("")
  </code></pre>