R help - Nov 2003 - plot map of areas

Hi all,

Given a number of points (x,y) in a plane, I'd like to plot a map of 
polygons, so that

    1) each polygon contains exactly one point
    2) the polygon defines the area for which this specific point is 
closer than any other point.

It's a bit like a map of areas "influenced" by that point, and
it's
obviously a matter of intersecting the perpendicular bisectors between 
adjacent points.

I believe this type of map has a name, but I can't remember how it's 
called.

Is there a function somewhere in a R package that may do this?

Thanks for your help

Pascal

Is the contributed package `deldir' on CRAN what you're looking for?

HTH,
andy
> From: Pascal A. Niklaus [mailto:Pascal.Niklaus at unibas.ch] 
> Hi all,
> 
> Given a number of points (x,y) in a plane, I'd like to plot a map of 
> polygons, so that
> 
>     1) each polygon contains exactly one point
>     2) the polygon defines the area for which this specific point is 
> closer than any other point.
> 
> It's a bit like a map of areas "influenced" by that point,
and it's
> obviously a matter of intersecting the perpendicular 
> bisectors between 
> adjacent points.
> 
> I believe this type of map has a name, but I can't remember how
it's
> called.
> 
> Is there a function somewhere in a R package that may do this?
> 
> Thanks for your help
> 
> Pascal

On Fri, 21 Nov 2003, Pascal A. Niklaus wrote:
> Hi all,
> 
> Given a number of points (x,y) in a plane, I'd like to plot a map of 
> polygons, so that
> 
>     1) each polygon contains exactly one point
>     2) the polygon defines the area for which this specific point is 
> closer than any other point.
> 
> It's a bit like a map of areas "influenced" by that point,
and it's
> obviously a matter of intersecting the perpendicular bisectors between 
> adjacent points.
> 
> I believe this type of map has a name, but I can't remember how
it's
> called.
> 
> Is there a function somewhere in a R package that may do this?
Try this:
> library(tripack)
> coords <- cbind(runif(100), runif(100))
> plot(coords, pch=19, col="blue")
> plot(voronoi.mosaic(coords[,1], coords[,2], duplicate =
"remove"),
+   add=TRUE)
> 
A Voronoi diagram? There are quite a lot of relevant functions in the 
tripack package. 
> 
> Thanks for your help
> 
> Pascal
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
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> 
-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: Roger.Bivand at nhh.no

"Pascal A. Niklaus" <Pascal.Niklaus at unibas.ch> writes:
> Hi all,
> 
> Given a number of points (x,y) in a plane, I'd like to plot a map of
> polygons, so that
> 
>     1) each polygon contains exactly one point
>     2) the polygon defines the area for which this specific point is
> closer than any other point.
> 
> It's a bit like a map of areas "influenced" by that point,
and it's
> obviously a matter of intersecting the perpendicular bisectors between
> adjacent points.
> 
> I believe this type of map has a name, but I can't remember how
it's
> called.
Voronoi Tesselation, unless my memory is failing me (again...)
 
> Is there a function somewhere in a R package that may do this?
package deldir will do VTs.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
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