Hi, Thanks, I must be remembering something else then. I hope I am not APOE4 +/+.
Nicholas On Sun, 17 Jan 2010 17:44 +0100, "Edzer Pebesma" <edzer.pebe...@uni-muenster.de> wrote: > Nicholas, > > this is unlikely; if true, the author would have done well to update his > software page http://www.cs.manchester.ac.uk/~toby/alan/software/ and > the corresponding wikipedia entry, > http://en.wikipedia.org/wiki/GPC_General_Polygon_Clipper_Library > > Even (some) universities can these days be very picky with licensing > when someone at the administration level smells money revenues from > software developed by one of the employees; they might claim that > anything produced by the employees in work time is owned by the > university. > > Best wishes, > -- > Edzer > > Nicholas Lewin-Koh wrote: > > Hi Roger, > > I thought I remembered that at some point you had contacted the author > > of gpclib and gotten permission to release the package under gpl. Has > > that changed or is senility completely catching up with me. > > > > Nicholas > > > > > > > >> Date: Fri, 15 Jan 2010 20:00:30 +0100 (CET) > >> From: Roger Bivand <roger.biv...@nhh.no> > >> To: rick reeves <ree...@nceas.ucsb.edu> > >> Cc: "r-sig-geo@stat.math.ethz.ch" <r-sig-geo@stat.math.ethz.ch> > >> Subject: Re: [R-sig-Geo] Alternate methods: Polygon Algebra / Polygon > >> Overlay with R Spatial objects.. > >> Message-ID: <alpine.lrh.2.00.1001151932080.18...@reclus.nhh.no> > >> Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII > >> > >> On Fri, 15 Jan 2010, rick reeves wrote: > >> > >> > >>> Hello List: > >>> > >>> I have been reviewing techniques within R for performing the GIS-like > >>> operation 'polygon algebra' (computing the union and intersection of > >>> polygons within two SpatialPolygonDataFrame objects). The goal is to > >>> combine two polygon data frames, to produce a new polygon data frames > >>> that contain the union or intersection of the two input sets. > >>> > >>> Thus far, the only method that I have found for this is the > >>> combinePolys() method within the PBSmapping package. The PBSmapping > >>> routines work well, but require the transformation out of the > >>> SpatialXXXDataFrame classes. > >>> > >> For union, aka dissolve, see unionSpatialPolygons() in maptools. Perhaps > >> better, don't look yet. The underlying problem is the license of the > >> gpclib package, which should be avoided. The reason for attention to > >> package licenses is that CRAN is getting very large, and taking > >> responsibility for distributing non-free software through package > >> dependencies needs to be automated. So GPL and other free packages should > >> not depend on or suggest non-free packages, because users (including > >> commercial users) may not be aware that they are using packages with > >> non-free licences. Some of these users already block the installation of > >> free packages with "upstream" non-free dependencies, and more will do so > >> in the future. > >> > >> One solution is the R-Forge rgeos package, which I'm working on. > >> > >> https://r-forge.r-project.org/projects/rgeos/ > >> > >> Before long, again thanks to Uwe Ligges and others, we should have a > >> working production line for Windows binary packages with GEOS 3.1.1 > >> included. Linux distributions have binaries or can install from source; > >> OSX has a Kyngchaos framework to handle the external dependency on GEOS. > >> > >> rgeos has unionSpatialPolygonsGEOS(), which, when rgeos reaches CRAN, > >> will > >> be used by maptools in unionSpatialPolygons() if rgeos is available. > >> > >> GEOS has the necessary functions to do what you would like, but someone > >> has to write the R and C code and add it to rgeos. The current > >> SpatialLinesIntersections() function returns a SpatialPointsDataFrame > >> object with the IDs if the intersecting lines, but more is needed for > >> SpatialPolygons intersection. The handling of the data frame variables is > >> far from obvious too - just copying across count or rate variables isn't > >> appropriate. Most likely the handling of the data slots would have to be > >> done by hand for the new SpatialPolygons objects based on the > >> intersecting > >> ID values. > >> > >> R-Forge has the possibility for new developers to join projects ... > >> > >> Hope this helps, > >> > >> Roger > >> > >> > >>> The overlay() method within sp seems like the best routine for this job > >>> as it > >>> performs intersection operations on pairs of Spatial objects, but it > >>> does not appear to operate on two SpatialPolygonDataFrame objects. > >>> So I have not tried to use it for this. > >>> > >>> Do other packages contain polygon algebra routines that operate on the > >>> Spatial classes? > >>> If not, are there any alternatives to the PBSmapping methods? > >>> > >>> Thanks, > >>> Rick R > >>> > >>> > >>> > >>> > >>> > >> -- > >> 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 > >> > >> > >> > >> ------------------------------ > >> > >> _______________________________________________ > >> R-sig-Geo mailing list > >> R-sig-Geo@stat.math.ethz.ch > >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo > >> > >> > >> End of R-sig-Geo Digest, Vol 77, Issue 13 > >> ***************************************** > >> > > > > _______________________________________________ > > R-sig-Geo mailing list > > R-sig-Geo@stat.math.ethz.ch > > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > > > > -- > Edzer Pebesma > Institute for Geoinformatics (ifgi), University of Münster > Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251 > 8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de > http://www.52north.org/geostatistics e.pebe...@wwu.de > _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo