[GRASS-user] Grass, Python, mapcalc

S. Koukoulas (lists) sotkouklistes at gmail.com
Fri Dec 28 06:02:31 PST 2012

Dear Paul,

having said all that for r.mapcalc, I wonder whether you really need
mapcalc. In your case,
couldn't you just use the * r.series * command with Sum (and perhaps 
g.mlist can help you make a list of all the daily maps).

I think that it might be faster as well.

On 12/28/2012 03:08 PM, Paul Meems wrote:
> Thanks Sotiris,
> I've tried your suggestion but converted it to Python because I'm on
> Windows.
> This is my script:
> grass.run_command('g.mremove', rast = ('out*'))
> grass.mapcalc('sun=global1', quiet=False, verbose=False, overwrite=True)
> for x in range(2, 10, 1):
>   exp = 'out=sun+global' + str(x)
>   print exp
>   grass.mapcalc(exp, quiet=False, verbose=False, overwrite=True)
>   grass.run_command('g.rename', flag='o', rast = ('out','sun'))
> This doesn't result in the expected outcome.
> sun is equal to global1 and no values are added
> out is global1+global2 but is no more values are added. But mapcalc is
> called several times.
> I've tested this with:
> r.what --v -f -n input=global1 east_north=156287.225281,383024.737026
> r.what --v -f -n input=sun east_north=156287.225281,383024.737026
> r.what --v -f -n input=out east_north=156287.225281,383024.737026
> Not only am I a new user to GRASS but I'm also still a novice in
> Python. Most likely it is something in my script.
> If somebody has a different approach to get the solar radiation of a
> whole year I'm happy to try that.
> Thanks,
> Paul
>     Date: Fri, 28 Dec 2012 14:36:15 +0200
>     From: "S. Koukoulas (lists)" <sotkouklistes at gmail.com
>     <mailto:sotkouklistes at gmail.com>>
>     To: grass-user at lists.osgeo.org <mailto:grass-user at lists.osgeo.org>
>     Subject: Re: [GRASS-user] Grass, Python, mapcalc
>     Message-ID: <50DD923F.806 at gmail.com <mailto:50DD923F.806 at gmail.com>>
>     Content-Type: text/plain; charset=windows-1252
>     To my experience with r.mapcalc you cannot do what yo do with
>     programming languages... e.g. i=i+1 will not work directly.
>     Instead you
>     could try a more indirect way, something like (here is an example with
>     bash shell script):
>     #g.mremove rast=out* (to remove previous stuff, if needed)
>     r.mapcalc sun=global1
>     for a in ?seq 2 10?; do
>     r.mapcalc out = sun + global$a
>     g.rename --o rast=out,sun
>     done
>     basically the main idea is to use an intermediate map and then before
>     the loop ends, pass it (with g.rename) to the map variable you want.
>     There might be a more elegant way with python, but hopefully this
>     shell
>     script example might help you.
>     HTH,
>     sotiris
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