[GRASS-user] compositing rasters

[Dave Roberts]

Colleagues,

    I know this must be easy, but I haven't found it.

    Suppose I have three grids (a, b, and c) where each grid is 0 or 1, 
and the 1s are mutually exclusive.  I want a new grid where if grid
a=1 then newgrid = 1; if grid b=1 then new grid = 2; if grid c=1 then 
newgrid = 3.

     Something like  r.mapcalc "new=if(a,1) || if(b,2) || if(c,3)"

seems like it ought to work but I can't seem to use multiple input file 
that way.

Thanks in advance for any help, Dave
-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
David W. Roberts                                     office 406-994-4548
Professor and Head                                      FAX 406-994-3190
Department of Ecology                         email droberts at montana.edu
Montana State University
Bozeman, MT 59717-3460