Perfect. Thanks very much. Also thanks for kind reminding on getting
the centroids of polygons.

2009/11/28 Roger Bivand <Roger.Bivand@nhh.no>

> On Fri, 27 Nov 2009, rusers.sh wrote:
>
>  Dear Robert,
>> My method to generate the Voronoi tessellation maybe not better, You can
>> show me you method to get it.
>>  What i want to get is the the class of SpatialPolygons(sp) based on the
>> generated Voronoi tessellation.
>>  Any ideas or suggestions are greatly appreciated.
>>
>
> In the list archives for March 2007 (search in Nabble, for example), there
> are hints. A more up to date version might be:
>
> set.seed(1)
> crds <- cbind(runif(100), runif(100))
> library(deldir)
> z <- deldir(crds[,1], crds[,2])
> w <- tile.list(z)
> library(sp)
> polys <- vector(mode="list", length=length(w))
> for (i in seq(along=polys)) {
>  pcrds <- cbind(w[[i]]$x, w[[i]]$y)
>  pcrds <- rbind(pcrds, pcrds[1,])
>  polys[[i]] <- Polygons(list(Polygon(pcrds)), ID=as.character(i))
> }
> SP <- SpatialPolygons(polys)
> SPDF <- SpatialPolygonsDataFrame(SP, data=data.frame(x=crds[,1],
>  y=crds[,2], row.names=row.names(SP)))
>
> plot(SPDF)
> points(crds, pch=3, col="red")
> text(coordinates(SPDF), label=row.names(SPDF))
>
> then export the SpatialPolygonsDataFrame in the usual way.
>
> By the way, to get the centroids (aka label points) for Polygons objects,
> use coordinates() on their enclosing SpatialPolygons object. The (very)
> deprecated maptools function you refered to in an earlier posting will cease
> to be available very shortly.
>
> Hope this helps,
>
> Roger
>
>
>
>> 2009/11/27 rusers.sh <rusers.sh@gmail.com>
>>
>>   Yes, what i want is really the Voronoi tessellation that you showed in
>>> the link. I can generate the Voronoi tessellation  (see my codes), but my
>>> problem is how to generate the the class of SpatialPolygons(sp) based on
>>> the
>>> generated  Voronoi tessellation? (SHP means shape file of polygon.)
>>>  Thanks a lot.
>>> ####My code to get the Voronoi tessellation########
>>> library(spatstat)
>>> win<-owin(c(0,1),c(0,1))
>>> pp <- runifpoint(10,win=win)
>>> #plot(pp)
>>> library(tripack)
>>> vm <- voronoi.mosaic(pp$x,pp$y)
>>> plot(vm)
>>> par(new=T)
>>> points(pp$x,pp$y,col='blue')
>>> axis(1,xlim=c(0,1)) #1=below
>>> axis(2,ylim=c(0,1)) #2=left
>>> box(xlim=c(0,1),ylim=c(0,1))
>>>
>>> 2009/11/27 Robert J. Hijmans <r.hijmans@gmail.com>
>>>
>>> I think you want a Voronoi tessalation (diagram):
>>>
>>>> http://en.wikipedia.org/wiki/Voronoi_diagram
>>>>
>>>> But what are SHP polygons?  Is 'SHP' a class in an R package?
>>>>
>>>> Robert
>>>>
>>>> On Fri, Nov 27, 2009 at 2:03 PM, rusers.sh <rusers.sh@gmail.com> wrote:
>>>>
>>>>>  To make this problem more clear. Suppose i have some points in a
>>>>>
>>>> certain
>>>>
>>>>> area (e.g. 10 points in a unit square), how to cut and generate the
>>>>> corresponding SHP polygons of containing the points (1 point in 1
>>>>>
>>>> polygon,
>>>>
>>>>> maybe the point as their centroid) in this certain area?
>>>>>  In GeoDa, there is a menu "tools->shape->point  to polygon" to achieve
>>>>> that. I wonder how to do that in R. Thanks a lot.
>>>>> ##Example##
>>>>> win<-owin(c(0,1),c(0,1))
>>>>> pp <- runifpoint(10) #generate 10 points
>>>>> #i want to change these 10 points into 10 SHP polygons,something like
>>>>>
>>>> the
>>>>
>>>>> manipulation in GeoDA, "tools->shape->point  to polygon"
>>>>> #plot(pp)
>>>>>
>>>>> 2009/11/27 rusers.sh <rusers.sh@gmail.com>
>>>>>
>>>>>  Hi,
>>>>>>  I always need to convert between the points and polygons. For
>>>>>>
>>>>> converting
>>>>
>>>>> the polygons to points, we can use the "get.Pcent(maptools) " to get
>>>>>>
>>>>> the
>>>>
>>>>> centroids of the polygons. But for converting points to polygons
>>>>>>
>>>>> (something
>>>>
>>>>> like GeoDa's "tools->shape->point  to polygon"), i cannot find the
>>>>>> corresponding method. I searched in R Site Search with "point to
>>>>>>
>>>>> polygon"
>>>>
>>>>> and "generate polygon", but still cannot get the answers.
>>>>>>  Does anybody know how to convert points to the SHP polygons?
>>>>>>  OR whether we can generate some SHP polygons randomly in R?
>>>>>> ##Example##
>>>>>> win<-owin(c(0,1),c(0,1))
>>>>>> pp <- runifpoint(10) #generate 10 points
>>>>>> #i want to change these 10 points into 10 SHP polygons,something like
>>>>>>
>>>>> the
>>>>
>>>>> manipulation in GeoDA, "tools->shape->point  to polygon"
>>>>>> #plot(pp)
>>>>>>  Thanks a lot.
>>>>>>
>>>>>>
>>>>>> --
>>>>>> -----------------
>>>>>> Jane Chang
>>>>>> Queen's
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> -----------------
>>>>> Jane Chang
>>>>> Queen's
>>>>>
>>>>>       [[alternative HTML version deleted]]
>>>>>
>>>>> _______________________________________________
>>>>> R-sig-Geo mailing list
>>>>> R-sig-Geo@stat.math.ethz.ch
>>>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>>>>
>>>>>
>>>>
>>>
>>>
>>> --
>>> -----------------
>>> Jane Chang
>>> Queen's
>>>
>>>
>>
>>
>>
>>
> --
> 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@nhh.no
>
>


-- 
-----------------
Jane Chang
Queen's

	[[alternative HTML version deleted]]

