[GRASS-user] null values

[Glynn Clements]

goldneaa at onid.orst.edu wrote:

> Lets say I have a map with a range of -20, and 20.  I am able to  
> create a legend that only shows -10,10.  But I want my map to only  
> show values from -10,10.  Is there a way to make the areas that are  
> above 10, or below -10 show up as white or null values on the display  
> map.  I have been playing around with val. list in d.rast.  But I have  
> not had much sucess in creating maps that take out my max and min  
> outliers.  Any suggestions?

If the maps are integer-valued, use r.reclass to map the undesired
categories to null.

If the maps have floating-point values, use r.mapcalc instead.

While the r.mapcalc approach will work for integer values, it copies
the map data, while r.reclass only need to store the reclass rules.

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