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 us

Answer 1

Following up on @Andy's answer, you could merge country polygons within each continent like so:

library(rworldmap)
library(rgeos)
library(maptools)
library(cleangeo)  ## For clgeo_Clean()

sPDF <- getMap()
sPDF <- clgeo_Clean(sPDF)  ## Needed to fix up some non-closed polygons 
cont <-
    sapply(levels(sPDF$continent),
           FUN = function(i) {
               ## Merge polygons within a continent
               poly <- gUnionCascaded(subset(sPDF, continent==i))
               ## Give each polygon a unique ID
               poly <- spChFIDs(poly, i)
               ## Make SPDF from SpatialPolygons object
               SpatialPolygonsDataFrame(poly,
                                        data.frame(continent=i, row.names=i))
           },
           USE.NAMES=TRUE)

## Bind the 6 continent-level SPDFs into a single SPDF
cont <- Reduce(spRbind, cont)

## Plot to check that it worked
plot(cont, col=heat.colors(nrow(cont)))

## Check that it worked by looking at the SPDF's data.frame
## (to which you can add attributes you really want to plot on)
data.frame(cont)
#                   continent
# Africa               Africa
# Antarctica       Antarctica
# Australia         Australia
# Eurasia             Eurasia
# North America North America
# South America South America