Roger, I got the package. This is great. Thank you very much, I will have a test run very soon. Have a nice weekend!
X.W. On Thu, Apr 9, 2009 at 2:42 PM, Roger Bivand <roger.biv...@nhh.no> wrote: > On Thu, 9 Apr 2009, x wong wrote: > > I do use Windows, and thank you very much for the help! >> >> I know how to do this in GIS as Jonathan suggested; however, I haven't >> tried >> it in R with the solution Rick recommended since i am still cleaning my >> input data. >> >> The problem of this task is very obvious: it will be super inefficient if >> all the distances have to be calculated. My initial thought was to locate >> the target points and subset the dataset before any calculations being >> made, >> but it may require quite a bit coding...... What you described sounds >> great >> to me, and i am looking forward to seeing it. >> >> b.t.w. the link you provided doesn't work, would you please double check >> it? >> > > The link works: > > http://spatial.nhh.no/R/etc/ann* > > means look in: > > http://spatial.nhh.no/R/etc/ > > for all files with names beginning with ann. The build for R 2.8.* is at: > > http://spatial.nhh.no/R/etc/ann_0.3-2.zip > > You will have to subset your data into two matrices of planar coordinates, > one matrix for the data= argument, the other for the query= argument to > ann(). The output object contains the k nearest neighbours in data= for each > point in query=, and their distances. See ?ann after installing the package. > > Roger > > > >> X.W. >> >> >> >> >> >> >> On Thu, Apr 9, 2009 at 3:07 AM, Roger Bivand <roger.biv...@nhh.no> wrote: >> >> On Wed, 8 Apr 2009, x wong wrote: >>> >>> 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 >>>>> >>>>> >>>>> Note that this will be inefficient in that it calculates all the >>> distances. >>> I have an off-CRAN package interfacing ANN, which - given two sets of >>> points, returns the k nearest in the first set (with distances) for each >>> point in the second set. ANN builds a tree of the first set, so searches >>> for >>> nearest neighbours efficiently. Look for: >>> >>> http://spatial.nhh.no/R/etc/ann* >>> >>> The Windows binary wasn't built for the current release of R, so probably >>> needs rebuilding - let me know if you use Windows, and I'll re-build it. >>> >>> Hope this helps, >>> >>> Roger >>> >>> >>> >>> 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 >>>> >>>> >>>> -- >>> 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.biv...@nhh.no >>> >>> >>> >> > -- > 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.biv...@nhh.no > > [[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
