[R] "Maps in R"

Baz B.Rowlingson at lancaster.ac.uk
Tue Feb 22 12:17:48 CET 2000

 I've just spent a couple of idle weekends getting a version of the
S-plus 'maps' library working under R.

 For those unfamiliar with the maps library, it lets you map a 
geographical region, split into areas, and optionally colour-fill
those areas according to some variable. For example:

R> library(maps)
R> map("state",c("california","nevada","washington"))

 draws a line map of those three states.

R> map("uk",fill=T,color=pop.colour)

 draws a map of the uk with counties coloured by the pop.colour

 The system also supports map projections. You can do this:

R> map("state",proj="merc")

 to draw the map on a mercator projection. I have used the USGS
PROJ4.2 projection library, and so there are many projections
and options available. I've also added a Great Britain Ordnance
Survey grid projection to PROJ4.2, for use with maps of this

 You can also do inverse projections - plot a map with a projection,
get locations with locator(), and then inverse-project them to get
back to lat-long coordinates.

 That's all the good news. The bad news is that there's a few problems
here and there, mainly related to lines that cross the +180/-180
and to certain projections - an azimuthal projection (i.e. as you would
see the earth from space) of the world map doesn't do hidden-line 
removal of the far side, it just crashes!

 So I'm looking for interested parties to have a play with the code.
Preferably people with some experience of the S/Splus maps library, or
anyone with a geographical interest. It may even be worth starting from
scratch again and building an R-GIS package from the ground up...

 Email me with your interest.

Barry Rowlingson
Maths and Stats
Lancaster University
Lancaster, UK
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