Re: [GRASS-user] Problems with r.mapcalc

[Micha Silver]

On 07/16/2013 04:28 PM, Elisa Dal Maso wrote: Hi, I'm a PhD student in Italy and I am a new user of GRASS. I have a problem in a weighted average with r.mapcalc. There are 3 raster map (areas of species), with different extent but the same resolution, area has value 1, outside is null *. I would like to sum these areas with different weights (10, 9 and 4), then divide for the sum of weights (23), generating a float, and I have used this formula: (10.*if(isnull(Fraxinus_excelsior_raster@Phalaen), 0, 1)+9.*if(isnull(Fraxinus_angustifolia_raster@Phalaen), 0, 1) +4.*if(isnull(Fraxinus_ornus_raster@Phalaen), 0, 1))/23. Instead of the "isnull()" functions, just set null to '0' with r.null for each raster before your mapcalc _expression_: i.e. r.null Fraxinus_excelsior_raster null=0 same for each of the other Fraxious* ... then, be sure you have set the region correctly: g.region rast=`g.mlist type=rast pattern="Frax*" separator=,` and finally r.mapcalc "weighted =  (Fraxinus_excelsior_raster * 10.0 + ....+ ....)/23.0" The resulting map have only 4 rectangles but it considers the sum of all the map (null values comprised). How could I resolve the problem? Thanks a lot!!! Elisa This mail was received via Mail-SeCure System. _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user This mail was received via Mail-SeCure System.

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