Singlepart to multipart

R-sig-geo'ers:

If I have a SpatialPolygonsDataFrame with a field "MYID", how do I go about
coercing that object to a multipart polygon, where I am "merging" on the
MYID field?

maptools::unionSpatialPolygons() which calls rgeos::gUnaryUnion, so go to 
rgeos::gUnaryUnion first unless you have challenged geometries - if hole 
problems use maptools::checkPolygonsHoles first.

Hope this helps,

Roger

--j

Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
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