[GRASS-user] Error with r.mapcalc

[Glynn Clements]

António Rocha wrote:

> I have a Python script with the following:
>    # Conversion to at-sensor brightness temperature       
>     grass.mapcalc("$raster_file= $K2/log(($K1/$L)+1)", raster_file=raster_file, K2=K2, K1=K1,L= tempL)
>     grass.mapcalc("$raster_file= if($raster_file < 0, null(), $raster_file)", raster_file=raster_file)
> 
> When it runs the second grass.mapcalc I get the following error:
> ERROR: Unable to close raster map
> ERROR: An error occurred while running r.mapcalc
> 
> Why am I obtaining this error? and How can I avoid it?

Because you're using the same map as both input and output, which
won't work. Either use a temporary name for the intermediate map, or
replace the second grass.mapcalc call with r.null, e.g.:

	grass.run_command('r.null', setnull = '-2147483647--1')

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