Thank you very much, that is very helpful.
x.w. On Wed, Apr 8, 2009 at 12:47 PM, rick reeves <ree...@nceas.ucsb.edu> wrote: > Assuming that this dataset fits within the confines of R, this could be > done with sp package: spdistsN1() function > See attached sample solution: > > > http://nceas.ucsb.edu/scicomp/GISSeminar/UseCases/AssignClosestPointsR/AssignClosestPointsR.html > > Hope this helps! RR > > > Jonathan Greenberg wrote: > >> It seems that a raster-based approach would make more sense, rather than >> the hugely computationally inefficient approach you are suggesting -- how >> about using a least cost path or euclidean distance approach? Both are >> available in many GIS packages (ArcMap, GRASS GIS, etc...) >> >> --j >> >> x wong wrote: >> >>> dear all, >>> >>> >>> >>> I have a raster GIS map converted to points. Now, I am trying to >>> calculate >>> the nearest neighbor distance for every point to a cluster of points >>> within >>> this map. Since the number of points is more than two millions, I am >>> wondering whether there is a computation efficient way to do this. >>> >>> >>> >>> The following is what the data looks like: >>> >>> point_id,x_coord,y_coord,class >>> >>> 675,-821292,6896866,GL >>> >>> 738,-819294,6895866,GL >>> >>> 803,-819294,6894867,GL >>> >>> 804,-818295,6894867,GL >>> >>> 805,-817296,6894867,GL >>> >>> 806,-816297,6894867,RCK >>> >>> 873,-818296,6893867,GL >>> >>> 874,-817297,6893867,GL >>> >>> 875,-816298,6893868,RCK >>> >>> 876,-815299,6893868,RCK >>> >>> 877,-814300,6893868,RCK >>> >>> 878,-813300,6893868,GL >>> >>> 945,-817297,6892867,GL >>> >>> 946,-816298,6892868,RCK >>> >>> 947,-815299,6892868,RCK >>> >>> 948,-814300,6892868,RCK >>> >>> 949,-813301,6892868,GL >>> >>> 950,-812302,6892869,GL >>> >>> 951,-811303,6892869,GL >>> >>> 1021,-816298,6891868,RCK >>> >>> 1023,-814300,6891868,RCK >>> >>> 1024,-813301,6891869,GL >>> >>> 1025,-812302,6891869,GL >>> >>> 1027,-810304,6891869,GL >>> >>> 1028,-809305,6891870,GL >>> >>> 1029,-808306,6891870,GL >>> >>> 1098,-816299,6890868,RCK >>> >>> 1099,-815300,6890868,RCK >>> >>> 1100,-814301,6890868,GL >>> >>> 1101,-813302,6890869,GL >>> >>> ............................................ >>> >>> >>> >>> I want to calculate, for example, the nearest distances for all GL points >>> to >>> the RCK class. >>> >>> >>> >>> >>> >>> X.W. >>> >>> [[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 >>> >>> >> _______________________________________________ >> R-sig-Geo mailing list >> R-sig-Geo@stat.math.ethz.ch >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >> > > > -- > Rick Reeves > Scientific Programmer/Analyst and Data Manager > National Center for Ecological Analysis and Synthesis > UC Santa Barbara > www.nceas.ucsb.edu > 805 892 2533 > > [[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
