I think that r.to.vect wants to build a line structure, like river channels, but sees all the raster cells occupied, so no linear structure, and the advice to thin first is then appropriate. If this is connected to your question about calculating a measure of spatial autocorrelation for the raster data, then I suspect that you do not need polygons but rather points, where r.out.xyz may be helpful, followed by v.in.ascii if you will be using GRASS downstream, or if you want to emit a shapefile for GeoDa (another posting).
If you really want to calculate a measure of spatial autocorrelation for your raster, I suggest copying the raster to R with readRAST6, creating the neighbour list with dnearneigh() with max. distance the greater of ewres and nsres, and proceeding from there in the usual way. But please consider the inevitable fact that unless the resolution of your raster matches the "natural" support of the phenomenon of interest, the observed autocorrelation will certainly be driven by your having multiple neighbouring "observations" of each "entity", in addition to not having demeaned (detrended) the data. This means that any results will almost certainly be spurious. Hope this helps, Roger Milton Cezar Ribeiro wrote: > > Dear Grass-Gurus, > > I have a 2400x2200 raster image with values ranging > from 0.1 to 42, in float format. Now I need > vetororize the image, on the way that each pixel > come to be a polygon and the pixel value be stored as > attribute. > > I am trying to do this using: > r.to.vect input=temp71.img output=temp71_img_integer_vect_200m --o -b > > but grass return the following error messages: > > GRASS 6.4.0svn (newLocation):C:/GRASS-6-SVN/msys/home/mjfortin > r.to.vect > inpu > t=temp71.img output=temp71_img_integer_vect_200m --o -b > WARNING: Vector map <temp71_img_integer_vect_200m> already exists and will > be overwritten > WARNING: Table <temp71_img_integer_vect_200m> linked to vector map > <temp71_img_integer_vect_200m> does not exist > Extracting lines... > ERROR: Raster map is not thinned properly. > Please run r.thin. > By the way, I am running grass under a WinXp 64bit. > Any help are welcome. > > Cheers > > milton > brazil=toronto > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user > > ----- Roger Bivand Economic Geography Section Department of Economics Norwegian School of Economics and Business Administration Helleveien 30 N-5045 Bergen, Norway -- View this message in context: http://n2.nabble.com/problem-on-vectorizing-a-float-point-raster-tp3052124p3054013.html Sent from the Grass - Users mailing list archive at Nabble.com. _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
