How can I plot a continents map with R?

Question

There are many solutions to plot maps at country level, but in my case I want to print statistics at continent level.

The only thing that comes into my mind is to use the country level maps and use a list of countries for each continent, but I was wondering if there is any simple solution for this kind of maps. To implement my idea it would be like this:

## produce the world map
map()
## list of countries per continent
SA <- c("argentina", "bolivia", "brazil", "chile", "colombia", "ecuador", "guyana", "paraguay", "peru", "suriname", "uruguay", "venezuela")
map(regions = SA, fill=TRUE, add=TRUE)

Answer 1

library(sp) #Load your libraries
library(maptools)
#Download the continents shapefile
download.file("http://baruch.cuny.edu/geoportal/data/esri/world/continent.zip",
              "cont.zip")
#Unzip it
unzip("cont.zip")
#Load it
cont <- readShapeSpatial("continent.shp")
#Plot it
plot(cont,
     col=c("white","black","grey50","red","blue","orange","green","yellow")) 
#Or any other combination of 8 colors