[R-sig-Geo] How to add borders to a shapefile

[Felipe Carrillo]

Hi:
Could someone show me how to add state borders to a shapefile.
Please follow the bellow link to download it.Thanks

https://secure.filesanywhere.com/fs/v.aspx?v=897263875a6472a99baa

library(rgdal)
library(maptools)
dsn="C:/pathtoshapefile"
wolves.map <- readOGR(dsn=dsn, layer="PNW_wolf_habitat_grid")
cols<-heat.colors(16);cols
spplot(wolves.map, "PRED_SUIT", names.attr = "PRED_SUIT", col.regions=rev(cols),
    colorkey=list(space="bottom"), main = "Wolf Presence", as.table = TRUE)

 
Felipe D. Carrillo
Supervisory Fishery Biologist
Department of the Interior
US Fish & Wildlife Service
California, USA