[GRASS-user] Using a variable inside GRASS commands with Python code/ grass.mapcalc

[S. Koukoulas (lists)]

Well, not a python solution, but you might find it useful.
In Windows you could try the shell (command prompt) there as well:

First get a list of your observers in a file, say obspoints.txt

v.out.ascii input=myobs at user output=c:\obspoints.txt fs=, dp=2

then run the shell's FOR command (run a help for more on the syntax)
ALL must run in ONE LINE (and you must be running Grass in from the
command prompt should be somewhere in the menu):

FOR /F "tokens=1,2,3 delims=, " %i in (obspoints.txt) do r.los
--overwrite input=mydtm at user output=obs%k coordinate=%i,%j
(here tokens are the columns, X,Y,ID - and replace r.los with the newer
r.viewshed)

Then use g.mlist to make a list of your files
g.mlist pattern=’obs*’ mapset=user sep=,

and use the output of the list with r.series (method=sum) to get what
you want.

r.series --overwrite input=amap,bmap,... output=outshed method=sum

(in r.series manual page, it is suggested that you could use g.mlist
inside r.series but I have not managed to do it correctly -maybe someone
can explain better the use of quotes?)

HTH
sotiris

On 01/08/2013 06:53 PM, Brian Sanjeewa Rupasinghe wrote:
> Hi,
>
> Thanks again. Since i use GRASS 7.0, it will not work there. I do not
> think it can either be installed in GRASS for Windows through Add-on
> extensions. What about using grass.mapcalc to integrate each viewshed
> if there is a method of handling variables in it? If not how about
> using r.series with sum? Your advice is appreciated since i am
> pretty new to GRASS.
>
> On Tue, Jan 8, 2013 at 9:19 PM, Leonidas Liakos
> <leonidas_liakos at yahoo.gr <mailto:leonidas_liakos at yahoo.gr>> wrote:
>
>     Do you need cumulative viewshed analysis?
>     Maybe r.cva is for you:
>     http://www.ucl.ac.uk/~tcrnmar/GIS/r.cva.html
>     <http://www.ucl.ac.uk/%7Etcrnmar/GIS/r.cva.html>
>
>     ------------------------------------------------------------------------
>     *Απο:* Brian Sanjeewa Rupasinghe <jinkabs at gmail.com
>     <mailto:jinkabs at gmail.com>>
>     *Προς:* Anna Kratochvílová <kratochanna at gmail.com
>     <mailto:kratochanna at gmail.com>>; grass-user at lists.osgeo.org
>     <mailto:grass-user at lists.osgeo.org>
>     *Στάλθηκε:* 2:45 μ.μ. Τρίτη, 8 Ιανουαρίου 2013
>     *Θέμα:* Re: [GRASS-user] Using a variable inside GRASS commands
>     with Python code/ grass.mapcalc
>
>     Hi,
>
>     Many thanks. It worked for me. Then i have a similar problem in
>     GRASS.mapcalc. What i need next is to add viewshed of each
>     observer location cumulatively while looping through the observer
>     locations in order to have final integrated viewshed analysis map.
>     So i used the following command in Python (some code ommitted)
>
>     for i in:
>     grass.run_command('r.viewshed', input = rinput, output =
>     'viewshed', coordinate = [x,y], obs_elev = oelv, tgt_elev = th,
>     memory = 4098, flags = 'b', overwrite = True, quiet = True)
>
>     grass.mapcalc("viewshed_cum = viewshed + viewshed_cum", overwrite
>     = True, quiet = True)
>
>     It seems that expressions like sum = c + sum does not work inside
>     grass.mapcalc.Is <http://grass.mapcalc.is/> there any alternative
>     or other way around to get this done? I am using GRASS 7 in Windows 7.
>
>     Cheers, Brian
>
>     On Tue, Jan 8, 2013 at 1:25 PM, Anna Kratochvílová
>     <kratochanna at gmail.com <mailto:kratochanna at gmail.com>> wrote:
>
>         Hi Brian,
>
>         On Tue, Jan 8, 2013 at 6:51 AM, Brian Sanjeewa Rupasinghe
>         <jinkabs at gmail.com <mailto:jinkabs at gmail.com>> wrote:
>         > Hi all
>         >
>         > I am generating viewshed of each observer location by
>         iterating through a
>         > set of observer coordinate file through
>         > Python code in Windows 7 . Below is the python command used
>         in grass for
>         > each iteration. According to this, each time
>         > loop iterates, output is overwritten with the same name. Now
>         what i need is
>         > to keep each output of all the observer locations. For this,
>         i need to
>         > concatanate output name (i.e. 'viewshed' with loop index i
>         which will be
>         > 'viewshed' + str(i) ). How is that possible within
>         > this grass.run_command?
>         >
>
>         just set a variable within each loop and use it in the
>         run_command:
>         for i in ... :
>         out = 'viewshed' + str(i)
>         grass.run_command('r.viewshed', input = rinput, output = out, ...)
>
>
>         Regards,
>         Anna
>
>         > grass.run_command('r.viewshed', input = rinput, output =
>         'viewshed',
>         > coordinate = [x,y], obs_elev = oelv, tgt_elev = th, memory =
>         4098, flags =
>         > 'b', overwrite = True, quiet = True)
>         >
>         > Cheers, Brian
>         >
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>
>
>
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