[R-sig-Geo] intersection of two polygons

[Roger Bivand]

On Tue, 20 Mar 2007, Sebastien wrote:

> Dear helpers,
> 
> I need to find the intersection of two polygons. I have two overlapping 
> polygons and I want to find the polygon corresponding to the common 
> part. Is there a fonction, like unionSpatialPolygons which can do that. 
> I have converted my polygons to "owin" and use the function 
> 'intersect.owin' in the pachage spatstat but it returns a binary matrice 
> of class "owin" or I would prefer a polygon.

No, there is not. I think that joinPolys() in the PBSmapping package can
do this, and you can get to the PBS PolySet representation using
SpatialPolygons2PolySet() in the maptools package, but then you'd need to
get back again to SpatialPolygons, which would involve coding. The 
alternative of using gpclib like unionSpatialPolygons() would also 
involve coding.

Roger

> 
> Thanks for your help,
> 
> Sébastien Ollier
> 
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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