[GRASSLIST:5393] Re: r.mapcalc neighbourhood modifier

[Glynn Clements]

Paul Kelly wrote:

> I was wondering is it not possible to specify a variable in the
> neighbourhood modifier [] in r.mapcalc. E.g. I can write map[2,-1] but if
> I write something like map[offsetrow,offsetcolumn] I get:
> parse error, unexpected `VARNAME', expecting `INTEGER' or `'-''
> Parse error
> Is there a good reason for this / would it be possible to change it, or
> does anybody know a workaround for specifying the contents of any
> arbitrary cell using variables?

What sort of variable?

Bear in mind that r.mapcalc's "variables" are effectively entire maps;
the value may change from cell to cell.

If you are thinking in terms of scripting, you can just use the
shell's variables e.g.

	offsetrow=2
	offsetcolumn=-1
	r.mapcalc "out = map[$offsetrow,$offsetcolumn]"

OTOH, if you want something that will vary over the course of the
evaluation, then it isn't possible, and it isn't really feasible to
change r.mapcalc to make it possible.

-- 
Glynn Clements <glynn.clements at virgin.net>