Message-ID: <alpine.LRH.2.00.0812100842450.14432@reclus.nhh.no>
Date: 2008-12-10T07:45:30Z
From: Roger Bivand
Subject: subset point data set by distance ranges
In-Reply-To: <OFF70D9A0C.10DFF46E-ON8525751B.000C27A8-8525751B.000C27C6@usgs.gov>
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