[GRASS-user] using r.mapcalc

[Hamish]

Thomas Drüssler wrote:
> Hello everybody
> 
> please help me solving a problem concerning r.mapcalc:
> my intention is to calculate a new map consisting of two older ones.
> the one  shows  digitized elements( rocks), cat values are NULL or 1, 
> the other is a reclassified map(slope >50), with cat values 1 or NULL.
> 
> so i have 4 options:
> pixels, with only digitized elements, pixels with only slope elements,
> pixels with both and pixels without(NULL) the resulting map sould
> consist of these 4 categories. i already tried r.patch, but with no
> success, there was only one resulting category and NULL values.


To the others' explainations I'll add that it is often nice to use
r.support to give your new categories a label / meaning. Then when you
create a legend you don't need to figure out what you meant by "cat 3".


Hamish