[R-sig-Geo] adding ids and df to hexagonal polys ?

[Roger Bivand]

On Wed, 9 Sep 2009, Horacio Samaniego wrote:

> Hi,
>
> I am trying to understand the different data types in the sp package.
> However, I do not seem to get the way that spdf are built.
>
> For example, let say that I can build a hexagonal grid. That work just
> fine using
>
>> regio <- readShapePoly("regions.shp")
>> hpts <- spsample(regio,type="hexagonal",cells=30000)
>> hpoly = HexPoints2SpatialPolygons(hpts)
>
> I'm unclear about adding a df with IDs to this new SpetialPolygons class

library(maptools)
xx <- readShapePoly(system.file("shapes/sids.shp", package="maptools")[1],
  IDvar="FIPSNO", proj4string=CRS("+proj=longlat +ellps=clrk66"))
hpts <- spsample(xx, type="hexagonal", n=100)
hpoly <- HexPoints2SpatialPolygons(hpts)
o <- overlay(xx, hpts)
row.names(o) <- row.names(hpoly)
hpoly1 <- SpatialPolygonsDataFrame(hpoly, data=o)
summary(hpoly1)
spplot(hpoly1, "BIR74")

After making sure that the IDs agree, just use the constructor for
SpatialPolygonsDataFrame objects.

Hope this helps,

Roger

>
> I guess that I'm not understanding how ids are assigned... any hint
> would be appreciated
>
> thanks
>
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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