Create plot of West Africa using ggplot2 and data from Natural Earth repository.

West Africa Plot.R

#Load relevant pacakges
library(ggplot2)
library(maptools)
library(rgeos)
library(plyr)

#  Download and unzip the Natural Earth Country Polygon data
oldwd <- getwd()
tmp <- tempdir()
setwd(tmp)
url <- "http://www.naturalearthdata.com/http//www.naturalearthdata.com/download/50m/cultural/50m-admin-0-countries.zip"
dest <- paste(tmp,"\\tmp.zip",sep="")
download.file(url,dest)	#File is 1.3Mb
unzip(dest)

#	Read in the data to a SpatialPolygonsDataFrame and subset to West African countries
wld <- readShapePoly("ne_50m_admin_0_countries")
wa <- wld[c(21,22,43,44,81,82,84,144,151,158,160,190,195,213),]

#	Convert to data.frame for plotting with ggplot2
wa@data$id <- rownames(wa@data) # Explicitly identifies attribute rows by the .dbf offset
wa.df <- as.data.frame(wa)
gpclibPermit() # required for fortify method if rgeos is unavailable
wa.fort <- fortify(wa, region="id")
wa.gg <- join(wa.fort, wa.df,by="id")

#	Create the plot
p <- ggplot(wa.gg)+
	geom_polygon(aes(long,lat,group=group))+
	geom_path(colour="white",aes(long,lat,group=group),size=1.2)+
	coord_equal()+
	scale_x_continuous(name=expression(paste("Longitude (",degree,")")),limits=c(-18,4),expand=c(0,0))+
	scale_y_continuous(name=expression(paste("Latitude (",degree,")")),limits=c(4,17),expand=c(0,0))
print(p)
unlink(tmp,recursive=T)
setwd(oldwd)