[GRASS5] r.mapcalc and NULL question

[Eric G . Miller]

Or just use the if() construct in r.mapcalc.

echo 'streams.2 = if (isnull(streams),-9999,streams)' | r.mapcalc

or something like that.  I've used this more than a few times to create
mask layers.

On Mon, Jan 15, 2001 at 10:39:55AM -0700, William L. Baker wrote:
> You can use r.null to turn the nulls into zeroes,
> then use r.mapcalc to give values where there is a 0.
> But, maybe you were thinking it would be better to
> modify r.mapcalc to do this...
> 
> Bill Baker
> 
> -----Original Message-----
> From: Markus Neteler [mailto:neteler at geog.uni-hannover.de]
> Sent: Monday, January 15, 2001 11:04 AM
> To: grass5 developers list
> Subject: [GRASS5] r.mapcalc and NULL question
> 
> 
> Hi there,
> 
> maybe a r.mapcalc/NULL FAQ, but I don't get it...
> 
> Assume you have a streams map (streams contain values,
> other cells=NULL). 
> 
> Now I want to add some values *everywhere* using r.mapcalc, but 
> it is only added in those cells not containing a NULL value.
> 
> Any ideas how to overcome this problem?
> 
> Thanks in advance
> 
>  Markus
> 
 

-- 
Eric G. Miller <egm2 at jps.net>

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