[R] library maps for R

[Ross Ihaka]

On Sat, Nov 06, 1999 at 05:53:49PM +1100, Tim Churches wrote:
> Ray Brownrigg wrote:
> > 
> > Anybody interested in the S maps library for R?  I have ported a
> > limited version of the software for a Unix platform, and would be happy
> > to make it available for anybody interested.  If there is a lot of
> > interest then I will submit it to CRAN.  I know that Ross Ihaka is
> > working on a new version for R, which does not have some of the
> > limitations of the original S version.
> > 
> > My version does not do projections or thinning but will accept the
> > standard S[-Plus] database files (*.[GLN]).
> 
> Ray,
> 
> Yes please!I am trying to get to grips with GRASS which is excellent but
> definitely overkill for a quick choropleth map. Maps via R would be very
> handy.

I have a student who working on writing new code which provides
functionality equivalent to the Becker/Wilks maps library.  The code
provides access to the data in the format produced by Alan Wilks, and
allows for drawing and extraction of polygons and boundary lines.
Unlike the S code, we never suck in more than one polygon at a time so
it is possible to draw a full resolution world map.  We are
experimenting with a couple of forms of thinning.

In addition to this basic database handling, we also need to implement
projection clipping facilities.  This is slightly more complex and help
and advice from anyone who knows about cartography would be very welcome.
At present the plan is to use the USGS PROJ.4 package for projections
and to have a look at the clipping techniques use in GMT3.

For data, we are will use the original Becker-Wilks data, perhaps
updated to more modern boundaries using VMAP0.  In addition, I'd like
to add the ability to handle ESRI shapefiles and E00 data, because
there is so much data available in these formats.

I have had a look at the data files in GMT (aka GSHHS and WVS), and
it appears that the relative accuracy is very good, they can be out
by up to 1-2km.

I hope to have something to show within the next two weeks.

	Ross
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