get.canusamex.bds {M3}

Obtain map boundaries for Canada, USA, and Mexico

Description

Obtain map boundaries of Canada, USA, and Mexico, including state boundaries, in longitude and latitude coordinates.

Usage

get.canusamex.bds()

Details

Retrieves a data frame containing the coordinates (longitude and latitude) for drawing the boundaries of Canada, USA (including states), and Mexico. This function is intended to be called by the function get.map.lines.M3.proj; in practice, it should rarely be called directly by the user.

Value

Data frame specifying the polylines needed to plot the national (Canada, USA, Mexico) and state outlines. This matrix has two columns, with longitude in the first column and latitude in the second.

Author(s)

Jenise Swall

See Also

map, get.map.lines.M3.proj

Examples

## Set up a plotting region (in longitude/latitude) that includes an
## eastern portion of the Canada/USA border.
plot(c(-82,-67), c(39,49), type="n", xlab="Longitude", ylab="Latitude")
## Superimpose national boundaries from "world" database, which is
## fairly low-resolution (since it includes worldwide national boundaries).
map("world", regions="canada", add=TRUE)
## Now, if we try to superimpose the the USA state boundaries from the
## higher resolution "state" database, we have a conflict.  (See
## particularly the Maine border.)
map("state", add=TRUE, col="blue")
## The high-resolution national boundaries in database "worldHires" (in
## mapdata) also don't match up with the state lines.
map("worldHires", add=TRUE, col="magenta")

## Instead, we get the national boundaries (Canada, USA, Mexico) at
## high-resolution from database "worldHires" and the state boundaries
## (without the coastlines and national boundaries) from the "state"
## database.
dev.new()
plot(c(-82,-67), c(39,49), type="n", xlab="Longitude", ylab="Latitude")
lines(get.canusamex.bds())