António wrote: > I need to randomly select non-null cells from a given map. > I tried r.random.cells but I cannot define a maximum number > random cells and some selected random cells are not valid > values in my map. is there any other function to randomly > select cells from a raster?
r.to.vect to get a vector area coverage of your raster (do not use the -s flag), then v.random.cover from wiki addons then v.to.rast, and finally r.mapcalc to transfer values from source map to random cell map? (probably we/I should make a new wrapper script to do that automatically) or you might skip the last steps and just use v.random.cover's raster= option to sample the raster map directly. probably the best idea is to fix r.random's cover= option to loop until it has enough points. also if you will be doing a lot of geostats it is probably worth your while to learn about the GRASS<->R interface: http://grass.osgeo.org/wiki/R_statistics ... then the world is open to you. good luck, Hamish _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
