Dear Roger, I am not sure if I really need to convert my polygons to psp format. In fact I have a shapefile with polygons and a pair of points (x0,y0,x1,y1) and what I need is: (1) to checkout if the lines defined by (x0,y0,x1,y1) cross or not any polygon and (2) to identify which polygons were crossed by this line.
I obtained these (x0,y0,x1,y1) coordinates by computing the shortest distance between all polygons pairwise. Now I need to eliminate the "lines" which cross over polygons, and keep only those lines that "link" polygons without a overlap relationship betteen lines and polygons. I understand that it is a topological question, but I don´t know how to deal it on sp/maptools. Case you have other ideas, please, let me know. Regards a lot, miltinho ----- Mensagem original ---- De: Roger Bivand <[EMAIL PROTECTED]> Para: Milton Cezar Ribeiro <[EMAIL PROTECTED]> Cc: r-sig-geo@stat.math.ethz.ch Enviadas: Segunda-feira, 4 de Fevereiro de 2008 17:03:25 Assunto: Re: [R-sig-Geo] converting shapefile/polygon to psp On Mon, 4 Feb 2008, Milton Cezar Ribeiro wrote: > Dear all, > > I have some shapefiles which contents are polygons and I would like to > convert it to psp (spatstat) format, and after run crossdist.psp. I > tryed several times without success. Any idea? Look at the coercion function in maptools from SpatialPolygons to owin; see what needs to be changed to match psp; debug; contribute? Note that touching polygons fail the topology test in spatstat, as they should. Seeing how a psp works should't be hard, it is effectively as described in: https://stat.ethz.ch/pipermail/r-sig-geo/2008-January/003075 for making the lll matrix for distppll(), but as a data frame. You could use the marks to record which Polygons/Polygon object the segments belong to. Roger > > Miltinho > > > > para armazenamento! > > [[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: [EMAIL PROTECTED] para armazenamento! [[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
