[R] Fine Tuning Country Map

[Lorenzo Isella]

Dear All,
Please see the short script at the end of the email, which I assembled  
looking for bits and pieces on the web.
It essentially does what I need: it plots several countries as a  
color-coded map.
I just would like to fine-tune a bit the final image, in particular

(1) Select my own colors for "painting" the countries (i.e. associate  
manually a color to every level)
(2) Be able to control the position of the legend and the size of the  
character used in the legend itself.

Any suggestion is welcome.
Cheers

Lorenzo

################################################à

## you will need the sp-package
library('sp')

## load a file from GADM (you just have to specify the countries "special  
part" of the file name, like "ARG" for Argentina. Optionally you can  
specify which level you want to have
loadGADM <- function (fileName, level = 0, ...) {
     load(url(paste("http://gadm.org/data/rda/", fileName, "_adm", level,  
".RData", sep     = "")))
     gadm
}

## the maps objects get a prefix (like "ARG_" for Argentina)
changeGADMPrefix <- function (GADM, prefix) {
     GADM <- spChFIDs(GADM, paste(prefix, row.names(GADM), sep = "_"))
     GADM
}

## load file and change prefix
loadChangePrefix <- function (fileName, level = 0, ...) {
     theFile <- loadGADM(fileName, level)
     theFile <- changeGADMPrefix(theFile, fileName)
     theFile
}

## this function creates a SpatialPolygonsDataFrame that contains all maps  
you specify in "fileNames".
## E.g.:
## spdf <- getCountries(c("ARG","BOL","CHL"))
## plot(spdf) # should draw a map with Brasil, Argentina and Chile on it.
getCountries <- function (fileNames, level = 0, ...) {
     polygon <- sapply(fileNames, loadChangePrefix, level)
     polyMap <- do.call("rbind", polygon)
     polyMap
}

spdf <- getCountries(c("ITA","CHE","FRA", "DEU","BEL", "LUX"))

AP <- c("SLS","SLS", "NWS", "NSLS", "NSLS", "NWS")

spdf$AP <- as.factor(AP)

png("many-countries.png")
## print(spplot(spdf, "NAME_ENGLI"))
print(spplot(spdf, "AP"))
## plot(spdf)
dev.off()