adding new maps to map, mapdata, mapproj; archive of R-sig-geo

Hi,

Sorry if this has been covered somewhere.

Is there a writeup describing how new maps get added to map, mapdata,
mapproj?

The build mechanisms with Bourne shell and AWK scripts are described in 
the Bell Labs Research Reports listed in ?map. It can be done, but there 
may be viable alternatives if your data are already in a geographical data 
format, in particular using the sp package approach, and rgdal for 
input/output and projection.

What I'm trying to do is overlay polygons in latitude and
longitude onto these maps, then project them.  The associated things
you'd like to do with such overlays apply, e.g,. color them, use
different boundaries, etc.  Or perhaps there is also an overlay
mechanism?

By polygon overlay, do you mean just plot polygons on top of other data - 
see the sp classes and possibly spplot() - illustrated on:

http://r-spatial.sourceforge.net/gallery/

If you mean topological overlay (creating new geometries from combined 
existing geometries and assigning indices to them), you need a GIS or a 
spatially extended database. GRASS or PostGIS/PostgreSQL should get you 
some or most of the way.

Second, is there an online archive of r-sig-geo (or for that matter
r-help, etc) that can be searched for such questions?

R-sig-geo can be searched from RSiteSearch(), although searching on "map" 
is made more difficult because the word is used in many contexts.

Roger

Thanks,

- Jan



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Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no