map2SpatialPolygons' 'proj4string' in spmaps

On Wed, 15 Oct 2008, Sebastian P. Luque wrote:

On Wed, 15 Oct 2008 19:24:18 +0200 (CEST),
Roger Bivand <Roger.Bivand at nhh.no> wrote:

If the fill=TRUE argument to map() is omitted, the rings are not
built:

se.baffin <- map("worldHires", xlim=c(-70, -60), ylim=c(62, 69),
resolution=0, interior=FALSE, fill=TRUE, plot=FALSE) baff <-
map2SpatialPolygons(se.baffin,
IDs=se.baffin$names)[match("Canada:Baffin Island", se.baffin$names)]
plot(baff, axes=TRUE)

looks OK to me. Add the CRS later. I don't think that we know
definitely that WGS84 was used, WDBII seems to have been around since
1985. Try overlaying on GE, for example, to get a feel.

Do you know of any examples showing how one may close such rings,
based on a polygon?  Say we have a rectangle over the map object and
want to close the ring so we enclose all the land (or water)?

By hand, you need to insert coordinates into the coords slot of the
Polygon object of interest and re-generate it. A recent question on
the list about houses east of a road was handled this way (stitch the
bounding box to the road and use overlay()).

Otherwise look at the unionSpatialPolygons() code for ideas on
interfacing gpclib classes and methods (also in PBSmapping).