[R-sig-Geo] help with county map fill type

[Michael Denslow]

Dear List,

I am attempting to generate some county level species distribution maps for a publication. The idea is to show three different categories on one map; one for species A, one for species B and one for a county that has both.
Ideally I think some sort of hatching or pattern would be best. I am afraid that my grey scale example will not show up well in print.
In ?map, it says '... Extra arguments passed to polygon or lines'. However if I use the density or angle arguments, it doesn't work.
I am afraid that I am missing something obvious here, please help.

Thanks
Michael

library(maps)
data(stateMapEnv)

map('county', 'north carolina', 
	boundary = TRUE,
	lty = 1)

map('county', region = c('North Carolina,Watauga'), 
	fill = TRUE, col = 'grey80', add = TRUE)

map('county', region = c('North Carolina,Avery'), 
	fill = TRUE, col = 'grey50', add = TRUE)

map('county', region = c('North Carolina,Ashe'), 
	fill = TRUE, col = 'black', add = TRUE)

## try to use density and angle
map('county', region = c('North Carolina,Wilkes'), 
	density = 20,angle = 90, col = 'black', add = TRUE)


Michael Denslow

I.W. Carpenter Jr. Herbarium [BOON]
Appalachian State University
Boone, North Carolina U.S.A.

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