Hello ! I`m looking for a way to convert a grid with nominal values into polygons. Up to now I didn`t find a way to do this in R. Maybe someone can give me a hint.
Here is what I did: # I start with a xyz table with the coordinates and a factor variable as z-value. # The points were regularly spaced because they were converted from a grid to apply a statistical model in R str(dat) 'data.frame': 337842 obs. of 3 variables: $ soil_unit: Factor w/ 37 levels "12b","16b","3c",..: 1 1 1 2 2 2 2 2 2 2 ... $ X : num 4400098 4395378 4400358 4399438 4399638 ... $ Y : num 5578198 5563698 5578238 5564918 5565358 ... gridded(dat) = ~X+Y # to get a SpatialPixelsDataFrame # the following I found on this list to convert # grid objects to spatial polygon objects # see: http://www.mail-archive.com/[email protected]/msg06549.html dat <- as(dat, "SpatialPixels") dat <- as(dat, "SpatialPolygons") The problem is, that every SpatialPixel is converted to one polygon - in my case 337842 polygons. Isn`t there a way to convert a SpatialGridDataFrame or a SpatialPixelsDataFrame into a SpatialPolygonsDataFrame. Because I have nominal values the conversion has to consider the DateFrame, I think. But something like poly <- SpatialPolygonsDataFrame(dat, ...) gives an error message. Any help is very welcome. Thanks TIM ----------------------------------------------------------------------------------- Tim Häring Bavarian State Institute of Forest Research Department of Forest Ecology Hans-Carl-von-Carlowitz-Platz 1 D-85354 Freising E-Mail: [email protected] http://www.lwf.bayern.de _______________________________________________ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
