Friends,
I did get an off-list solution (thanks Jiao) that works for two
rasters but not for n (using the implied else).
I think what GRASS needs is an r.update routine that works like an
SQL update statement, i.e.
r.update map=composite.map value=1 where="map a = 1"
r.update map=composite.map value=2 where="map b = 1"
etc
This would solve my immediate problem but also have general
utility. I can export the grids and do it in FORTRAN easily enough, but
I haven't cracked the GRASS API yet to actually make a GRASS function
out of it.
Maybe there already is such a thing?
Thanks, Dave
On 12/31/2013 06:00 PM, Dave Roberts wrote:
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 [email protected]
Montana State University
Bozeman, MT 59717-3460
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