[R-sig-Geo] which function in R can extract the coordinats of ploygon's center and create Dirichlet tessellation/Delaunay triangulation of points?

Roger Bivand Roger.Bivand at nhh.no
Tue Mar 6 19:51:20 CET 2007

On Tue, 6 Mar 2007, zhijie zhang wrote:

> Dear friends,
>   I can't find the functions in R to do the following tasks:
> 1. extract the coordinats of ploygon's center  ;

The coordinate() method for a SpatialPolygons or SpatialPolygonsDataFrame 
object returns the centroid of the largest member polygon.

> 2. create Dirichlet tessellation and Delaunay triangulation for a set of
> points sp,spdep,tripack,et al, seem not to be able to finish it.

Please review the following recent posting, where the deldir package is 
used to extract a tesselation:


It ought to cover your question (it is more difficult to recover the outer 
polygons of the tesselation from tripack as closed polygons).

Hope this helps,


>  If u know how to do it, please let me know.
> Thanks very much.

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

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