[R-sig-Geo] subset point data set by distance ranges

[Roger Bivand]

On Tue, 9 Dec 2008, David M Warner wrote:

> Greetings
> I'm using R 2.8 with recent (last month) versions of the packages I need to
> use at present.
>  
> I'm interested in examining hierarchical spatio-temporal patterns in a data
> set.  The data consist of 94 points (X, Y, UTM coordinates) at which catch
> rates for a fish were recorded and there are also estimates of prey
> available for these fish at the same locations.  I have reason to believe
> that the relationships between predators and prey varies with spatial scale
> (nested processes).
>  
> To test this hypothesis, I'd like to generate subsets of the points that are
> separated by distance ranges (1-50 km, 51-100 km, etc) so I can run Sncf
> (package ncf) on the subsets.
>  
> I cannot find a way to do this with R code.  Getting a distance matrix is
> easy.  Using that to help generate a series of distance-based subsets is
> something I cannot figure out (without manually entering a list of all the
> point pairs).

Perhaps see dnearneigh() in spdep? It will return a list of vectors 
of point indices within the distance thresholds given, which you could 
post-process for your purposes.

Roger

>  
> Any suggestions would be appreciated.
> Dave Warner 
> David Warner
> Research Fishery Biologist
> USGS Great Lakes Science Center
> 1451 Green Road
> Ann Arbor MI 48105
> 734.214.9392
> 
>

-- 
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