[R] Adding labels on maps (using sp, maptools, or something else suggested)

[Misha Spisok]

Hello,

I would like to place region names (or abbreviations if space is too
limited) on a map.  I have tried the following, copying and adapting
various examples I have seen but without success.  The first example
is self-contained, but the second one requires the .shp file, which
can retrieved at http://www.gadm.org/country.

-----     Example 1     -----
library(sp)
con <- url("http://gadm.org/data/rda/ITA_adm1.RData")
print(load(con))
close(con)

regionnames <- c("Piemonte", "Valle d'Aosta", "Liguria", "Lombardia",
	"Trentino-Alto Adige/Südtirol", "Veneto", "Friuli-Venezia Giulia",
"Emilia-Romagna",
	"Toscana", "Umbria", "Marche", "Lazio", "Abruzzo", "Molise",
"Campania", "Puglia",
	"Basilicata", "Calabria", "Sicilia", "Sardegna")

gadm$regionnames <- as.factor(regionnames)
col = rainbow(length(levels(gadm$regionnames)))
spplot(gadm, "regionnames", col.regions=col, main="Italian Regions")

This gets me a map with regions colored, but I want uncolored regions
with the labels in 'regionnames' placed in the appropriate region.
Furthermore, the colors do not correctly match the names.  I suppose I
could manually re-order my regionnames vector, but that seems
avoidable in a way that I cannot see.  Finally, I do not want the
legend, as it would be meaningless for my use.

-----     Example 2     -----
library(maptools)
nc2 <- readShapePoly("ITA_adm1.shp")
plot(nc2)
invisible(text(getSpPPolygonsLabptSlots(nc2),
labels=as.character(regionnames), cex=0.4))

This gets me a map with regions outlined (as desired), but the names
don't land where I want them to.  A relatively "klunky" solution is to
just re-order them manually when I declare

regionnames <- c( etc ),

but I'd like to learn how to use what seems to be already available in
either the .shp or .dbf file.

Best,

misha