[GRASS-user] compositing rasters

[Tyler Smith]

Dave Roberts <dvrbts at ecology.msu.montana.edu> 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
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What about

r.mapcalc new=a + b*2 + c*3

If the maps are mutually exclusive, only one of the three will be non-zero for each cell.

Tyler
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