On Tue, 2008-11-11 at 19:34 -0800, John C. Tull wrote: > On Nov 11, 2008, at 6:45 PM, Hamish wrote: > > > John wrote: > >> I am creating a raster map that essentially summarizes the > >> intersection of a series of labeled rasters that each have > >> values of either 1 or null (presence/absence data). I am > >> using r.series like this to perform the summation across the > >> rasters that are all named with a prefix of presence_: > >> > >> r.series input="`g.mlist rast > >> pattern='presence_*' sep=,`" > >> output=presence_sum method=sum --o > >> > >> Can anyone think of a way to achieve this summation of > >> intersections in a way that will also allow for each cell to > >> have a label that concatenates all labels for the respective > >> raster maps that are present at that cell? E.g., let's > >> say three of the rasters are present at a particular cell, > >> and the labels for those rasters are 'raster1', > >> 'raster4', and 'raster7'. I would like the > >> final map to have a label of 'raster1, raster4, > >> raster7'. > >> > >> Any and all suggestions are greatly appreciated. > > > > > > the trick here is to r.reclass 0/1 absence/presence maps to be 0/2^n > > before running the sum. So you then get a sum like 13, which would > > mean > > the 8+2+1 maps were all present, or if the sum was 5 you'd know the > > 1+4 > > maps were present for that cell, and not others. > > > > > > see also r.bitpattern and r.mapcalc bitwise operators. (sorry I don't > > know the proper name/wikipedia link for this technique, I'm not a > > computer > > scientist) > > > > > > Hamish
That was my general idea... (well, more or less). But I did not think of r.bitmap as a possibility. Maybe there is away to do reverse-r.bitmap and "code"(=assign to) pixels with various values which will correspond to different categories-combinations(of maps). This is how the MODIS Quality Layers work more or less, right? Regards, Nikos _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
