How can I represent NULL values in r.mapcalc?
I mean, doing something like this:
r.mapcalc "test3 = if(test == NULL)"
Is there any doc explaining the use of the NULL values
in grass?
Thanks
Agus
Dr. Agustin Lobo
Instituto de Ciencias de la Tierra (CSIC)
Lluis Sole Sabaris s/n
08028 Barcelona SPAIN
tel 34 93409 5410
fax 34 93411 0012
alobo@ija.csic.es
http://pangea.ija.csic.es/alobo
Hello Agus !
There are two PS-Docs on the documentation page in Hannover, concerning
map algebra with r.mapcalc. These do only cover the old NULL values, not
the GRASS5 NULL and NO DATA values.
If you want r.mapcalc to create a raster map with only the NULL values of
an existing map, the <if> statement in r.mapcalc gives you several
options, how to be used (Right now, i do not know th eexactly syntax):
new_map = if (exist_map) : where exist_map not NULL, new_map gets 1
new_map = if (new_cat,exist_map) : -- " -- , new_map gets new_cat
there are more options, i do not remember them by heart. If you want to
use a logical not use the ^ sign (use this for your example:
"new_map=if(^ exist_map)", this should work).
Hope this helps, Greetings
Michael
==============================================================
Michael Schulz
Christoph-Mang-Str.5 Geologisches Institut
79100 Freiburg Universitaet Freiburg
Albertstr. 23b
79104 Freiburg
On Wed, 15 Sep 1999, Agustin Lobo wrote:
How can I represent NULL values in r.mapcalc?
I mean, doing something like this:
r.mapcalc "test3 = if(test == NULL)"
Is there any doc explaining the use of the NULL values
in grass?Thanks
Agus
Dr. Agustin Lobo
Instituto de Ciencias de la Tierra (CSIC)
Lluis Sole Sabaris s/n
08028 Barcelona SPAIN
tel 34 93409 5410
fax 34 93411 0012
alobo@ija.csic.es
http://pangea.ija.csic.es/alobo