[GRASS-user] v.to.rast, r.to.vect, "stable" transformation

[Glynn Clements]

Johannes Radinger wrote:

> Maybe I just see something wrong..anyway i thought about testing the
> stability in a loop, but I got stucked in the correct map calc
> operation.
> 
> What is the correct (boolean) operator to get:
> 1) NULL + NULL = NULL
> 2) not NULL + not NULL = NULL
> 3) not NULL + NULL = 1
> 4) NULL + not NULL = 1

	if(isnull(A) == isnull(B),null(),1)

-- 
Glynn Clements <glynn at gclements.plus.com>