[GRASS-user] scripting mapcalc

[Daniel Victoria]

Hi,

To get around the ' or " problems when scripting for r.mapcalc I
prefer to use another syntax construction that goes like this:

echo "river = if(river == $old, $new, null())" | r.mapcalc

That way you evaluate the variables $old and $new before sending it to
r.mapcalc.

cheers
Daniel

On Thu, Mar 5, 2009 at 11:42 AM, achim <ak7 at jupiter.uni-freiburg.de> wrote:
> Hi,
>
> did someone tried -like me- to use r.mapcalc in a script inside an
> do-while-clause?
>
> I cannot pass changing variables $old, $new like:
> r.mapcalc 'river=if(river=$old,$new,null())'
> its because of the '', which are needed because if the if-statement.
> I failed passing the hole statement eg. 'river=if(river=5,4,null())' as
> a variable like:
> r.mapcac $statement
> ...
>
> I tried many things and some shells (bash,csh,tcsh)...
>
> I think its because the ''. Besides when it seemed do be expressed the
> right way I got this answer:
>
> r.mapcalc 'river=if(river=4032076,4032075,null())' <-debugging output
> syntax error, unexpected $end, expecting '='
> Parse error
>
> or
>
> syntax error, unexpected '=', expecting ')'
> Parse error
>
> or
>
> Ungültiger Dateiname. Das Zeichen <=> ist nicht erlaubt.
> Ungültige Karte <if(river=4032076,4032075,null())>
> Parse error
>
> depending on what I tried.
>
> Can someone help?
>
> Or is there another (and faster) way to query raster-data without
> writing a C-Program?
>
> I'd like to do it inside grass. Otherwise I would export the map to
> octave to calculate there, but its not the gentle way I think.
>
> Thanks,
> achim
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