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## ###########################################################
## PURPOSE: Obtain outlines of Canada, USA, and Mexico, including
## state lines.
##
##
## INPUT: No input arguments.
##
##
## RETURNS: A list containing two elements "coords" and "units", The
## element "coords" contains a matrix with the map lines in the
## projection coordinates. The element "units" contains the units
## of the coordinates ("km" or "m").
##
##
## ASSUMES:
## Availability of R packages maps and mapdata.
##
##
## REVISION HISTORY:
## Original release: Jenise Swall, 2012-05-15
## ###########################################################
get.canusamex.bds <- function(){
## Get maps of Canada, USA, Mexico in high-resolution from mapdata
## package.
canusamex.natl <- map("worldHires", regions=c("Canada", "USA", "Mexico"),
exact=FALSE, resolution=0, plot=FALSE)
canusamex.natl.lonlat <- cbind(canusamex.natl$x, canusamex.natl$y)
rm(canusamex.natl)
## Get map of state borders, without including the outer boundaries.
## These outer boundaries are provided by the the high-resolution
## national maps created in the previous step.
state <- map("state", exact=F, boundary=FALSE, resolution=0, plot=FALSE)
state.lonlat <- cbind(state$x, state$y)
rm(state)
## Put it national and state boundaries together.
canusamex <- rbind(canusamex.natl.lonlat, matrix(NA, ncol=2), state.lonlat)
rm(canusamex.natl.lonlat, state.lonlat)
## Return the boundaries to the calling program/function.
return(canusamex)
}
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