[R-SIG-Mac]making maps a la usa()

[Phil Price]

I need to make some maps, showing states in the U.S. with highlighting, 
superimposed bars of adjustable length and width, etc...the sort of 
thing one would use usa() for in S.  An archive search finds that there 
are some platform-specific ports, but not for OS X.

I'm not sure why this is a platform-specific issue, really: it seems 
like usa() (and related map functions) could be written using R's 
graphics functions, and I'm kinda surprised if that's not the way it was 
originally done.

Is there an R solution for this?

Thanks.

--Phil Price
   Lawrence Berkeley National Laboratory