Lorenzo,
I'd suggest posting such questions to the R-sig-geo list, which seems
more suitable.
The book "Applied Spatial Data Analysis with R" written by Roger
Bivand, Edzer Pebesma and Virgilio Gómez-Rubio has exactly what you want.
http://www.amazon.com/Applied-Spatial-Data-Analysis-Use/dp/0387781706
Package classInt can help with colouring;
and about the legend: "The location may also be specified by setting x
to a single keyword from the list "bottomright", "bottom", "bottomleft",
"left", "topleft", "top", "topright", "right" and "center". This places
the legend on the inside of the plot frame at the given location.
Partial argument matching is used. The optional inset argument specifies
how far the legend is inset from the plot margins. If a single value is
given, it is used for both margins; if two values are given, the first
is used for x- distance, the second for y-distance."
Good luck!
Marcio
www.dsr.inpe.br/~mello
On 8/13/12 11:33 PM, Lorenzo Isella wrote:
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()
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and provide commented, minimal, self-contained, reproducible code.
