[R-sig-Geo] merging sp objects

[David Hugh-Jones]

The spRbind methods also complain about non-unique IDs. Is there any
other difference between them and rbind?


David Hugh-Jones
PhD Candidate
Essex University Department of Government
http://davidhughjones.googlepages.com


2008/7/1 Roger Bivand <Roger.Bivand at nhh.no>:
> On Tue, 1 Jul 2008, David Hugh-Jones wrote:
>
>> OK, writing
>> http://wiki.r-project.org/rwiki/doku.php?id=tips:spatial-data:merging,
>> a question comes up:
>>
>> I am trying to rbind() two SpatialLines (or SpatialPolygons or
>> whatever) objects and I keep getting the error that they have
>> overlapping IDs - not surprisingly as they were independently created.
>> Is there a simple way to give new IDs to these objects, and to know
>> how many I have to give?
>
> ?spChFIDs in maptools for the methods, but the choice of unique IDs will
> depend on your domain. The default readOGR IDs are the feature IDs, usually
> 0:(n-1), which will not be unique. If there are known official codes, like
> US FIPS codes, they can be used to disambiguate. You can use unique(c(IDs_A,
> IDs_B)) to proceed. Have you looked at spRbind methods in maptools as an
> alternative to rbind.* in sp?
>
> Roger
>
>>
>> David Hugh-Jones
>> PhD Candidate
>> Essex University Department of Government
>> http://davidhughjones.googlepages.com
>>
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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
>
>