[R] maps and lattice

[Sundar Dorai-Raj]

Jon Loehrke said the following on 2/5/2008 2:29 PM:
> Is it possible to place maps onto lattice plots?
> 
> With basic plotting you can add a map to a plot
> 
> library(lattice)
> long<-c(-69.2, -69.5, -70.1, -70.3)
> lat<-c(41, 41.5, 43.2, 42.8)
> plot(long, lat)
> map('state', c("massachusetts"),add=TRUE)
> 
> but is it possible with lattice?
> 
> 
> library(lattice)
> factor<-c(1,1,2,2)
> xyplot(lat~long|fact)
> ...now what?
> 
> I have looked at panel and found through google an extravagant shape  
> file export/import to R.
> Is there a simpler fix?
> 
> Thank you very much for your help.
> 
> Jon
> 
> School for Marine Science and Technology
> UMASS-Dartmouth
> 


Try this:

library(lattice)
library(maps)
long <- c(-69.2, -69.5, -70.1, -70.3)
lat <- c(41, 41.5, 43.2, 42.8)
fact <- c(1, 1, 2, 2)
xyplot(lat ~ long | fact,
        panel = function(...) {
          panel.xyplot(...)
          mp <- map("state", "massachusetts", plot = FALSE)
          lpolygon(mp$x, mp$y)
        })

HTH,

--sundar