[GRASS-user] r.mapcalc and the neighborhood modifier

Rainer M Krug Rainer at krugs.de
Tue Jul 16 03:50:57 PDT 2013


I would like to create a new raster layer, based on the neighborhood
modifier, but where the offset is not constant, but the cell value in a
different map.

Reasoning: I am modeling seed dispersal into neighboring cells and the
direction is based on the aspect. I created the aspect in agnps format
("flowdir") and I created two layers (flowdir_dx and flowdir_dy) indicating the x and y offset
based on flowdir.

Now when simulating the flow, I want to use:

| r.mapcalc expression="test = seeds[flowdir_dy, flowdir_dx]" --overwrite

but I get the following error:
| syntax error, unexpected NAME, expecting INTEGER or '-'
| Parse error
| ERROR: parse error
I assume from that error message, that I can not supply a map go get the
values for the neighborhood modifier, but have to use constant values.

I could put these into if statements, but I wanted to avoid these if

Is there a way that I can use the offset from a map?



Rainer M. Krug

email: RMKrug<at>gmail<dot>com
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