title: ggplot map with l
body: <p>I want to plot a world map using ggplot2 (v.9) which combines two pieces if information.  The following example illustrates:</p>
  
  <pre><code>library(rgdal)
  library(ggplot2)
  library(maptools)
  
  # Data from http://thematicmapping.org/downloads/world_borders.php.
  # Direct link: http://thematicmapping.org/downloads/TM_WORLD_BORDERS_SIMPL-0.3.zip
  # Unpack and put the files in a dir 'data'
  
  gpclibPermit()
  world.map &lt;- readOGR(dsn="data", layer="TM_WORLD_BORDERS_SIMPL-0.3")
  world.ggmap &lt;- fortify(world.map, region = "NAME")
  
  n &lt;- length(unique(world.ggmap$id))
  df &lt;- data.frame(id = unique(world.ggmap$id),
                   growth = 4*runif(n),
                   category = factor(sample(1:5, n, replace=T)))
  
  ## noise
  df[c(sample(1:100,40)),c("growth", "category")] &lt;- NA
  
  
  ggplot(df, aes(map_id = id)) +
       geom_map(aes(fill = growth, color = category), map =world.ggmap) +
       expand_limits(x = world.ggmap$long, y = world.ggmap$lat) +
       scale_fill_gradient(low = "red", high = "blue", guide = "colorbar")
  </code></pre>
  
  <p>However, this solution is not a nice way to display both <code>growth</code> and <code>category</code>.  <code>Growth</code> is highly visible, but <code>category</code> is almost impossible to see because it is just a border. </p>
  
  <p>I have tried to increase the size of borders, but without luck (the new geom_map is hard to work with).  Does anyone knows how to increase border size in the above example, <em>or</em> even better, a mechanism to display two factors?</p>
  
  <p><s>A bonus question: country names, such as those used by the maps package (which features USSR!) are the data used in the example is fragile.  I prefer to use ISO 3166-1 alpha-3(<a href="https://en.wikipedia.org/wiki/ISO_3166-1_alpha-3" rel="noreferrer">1</a>).  Does anyone know data readily usable with ggplot2 which features ISO-... country names</s> (included in linked data)</p>
  
  <p>Result:</p>
  
  <p><a href="http://ompldr.org/vY3hsYQ" rel="noreferrer">result http://ompldr.org/vY3hsYQ</a></p>