[GRASS-user] Getting statistical values (r.univar) via python

[Margherita Di Leo]

On Fri, May 25, 2012 at 1:46 PM, Johannes Radinger <JRadinger at gmx.at> wrote:

> Hi Madi,
>
> thank you, that's just what I thought of...
> anyway do you know does r.univar consider MASK if it is existing?
>

Yes it does.

madi

>
> /johannes
>
> -------- Original-Nachricht --------
> > Datum: Fri, 25 May 2012 13:38:05 +0200
> > Von: Margherita Di Leo <diregola at gmail.com>
> > An: Johannes Radinger <JRadinger at gmx.at>
> > CC: grass user list <grass-user at lists.osgeo.org>
> > Betreff: Re: [GRASS-user] Getting statistical values (r.univar) via
> python
>
> > Hi Johannes,
> >
> > On Fri, May 25, 2012 at 1:12 PM, Johannes Radinger <JRadinger at gmx.at>
> > wrote:
> >
> > > Hi,
> > >
> > > I am trying to get statistical values for a raster map in a python
> > script.
> > > What I am doing so far is using r.univar (e.g. for the nc-dataset):
> > >
> > > grass.read_command("r.univar", map ="elevation")
> > >
> > > but how to get e.g the mean value as float? I thought of two
> > > options:
> > >
> > > 1) either indexing like
> > > float(grass.read_command("r.univar", map ="elevation")[x:y])
> > >
> > > 2) or splitting the string into lines and then at the ":"
> > >
> > >
> > You can use the following:
> >
> > import sys
> > import os
> > import grass.script as grass
> >
> > univar = grass.read_command('r.univar', map='elevation')
> >
> > print univar #so that you can see how the output looks like
> >
> > The output is:
> > total null and non-null cells: 2025000
> > total null cells: 0
> >
> > Of the non-null cells:
> > ----------------------
> > n: 2025000
> > minimum: 55.5788
> > maximum: 156.33
> > range: 100.751
> > mean: 110.375
> > mean of absolute values: 110.375
> > standard deviation: 20.3153
> > variance: 412.712
> > variation coefficient: 18.4057 %
> > sum: 223510266.5581016541
> >
> > Now you want to split every line of the output with .split('\n'), you are
> > interested in the line [10], then you split against split(':') and take
> > the
> > argument [1].
> >
> > mean = float(univar.split('\n')[10].split(':')[1])
> >
> > Hope this helps,
> >
> > madi
> > --
> > Ing. Margherita Di Leo, Ph.D.
>
> --
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>



-- 
Ing. Margherita Di Leo, Ph.D.
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