[GRASS-dev] r.regression.multi failing

[Paulo van Breugel]

On Wed, Mar 23, 2016 at 4:57 PM, Markus Metz <markus.metz.giswork at gmail.com>
wrote:

> On Wed, Mar 23, 2016 at 4:43 PM, Paulo van Breugel
> <p.vanbreugel at gmail.com> wrote:
> >
> >
> > On 23-03-16 16:21, Moritz Lennert wrote:
> >>
> >> Le Wed, 23 Mar 2016 15:55:40 +0100,
> >> Paulo van Breugel <p.vanbreugel at gmail.com> a écrit :
> >>
> >>> On 23-03-16 15:24, Anna Petrášová wrote:
> >>>>
> >>>> On Wed, Mar 23, 2016 at 10:01 AM, Luca Delucchi
> >>>> <lucadeluge at gmail.com> wrote:
> >>>>>
> >>>>> On 23 March 2016 at 14:31, Paulo van Breugel
> >>>>> <p.vanbreugel at gmail.com> wrote:
> >>>>>>
> >>>>>> Hi,
> >>>>>>
> >>>>>
> >>>>> Hi,
> >>>>>
> >>>>>>
> >>>>>> I am using r.regression.multi in a python script (using
> >>>>>> grass.run_command()) to compute the variance inflation factor
> >>>>>> (VIF).  It runs in a loop, regressing variables one by one to all
> >>>>>> the other variables. It sometimes happen that the function fails
> >>>>>> with:
> >>>>>>
> >>>>>> WARNING: Matrix is unsolvable
> >>>>>> ERROR: Multiple regression failed
> >>
> >> This looks like a clear bug for me. So, even if I understand that you
> >> need to work around it for now, could you also post a bug report with a
> >> reproductible example ?
> >
> > Not sure it is a bug? It happens when amongst the independent variables
> > there are perfectly correlated variables. The message "WARNING: Matrix is
> > unsolvable" therefore seems correct to me.
>
> Yes, this warning should only occur in case of colinearity
>
> > Now this is treated as an error
> > (ERROR: Multiple regression failed"), which I guess is the equivalent of
> > grass.error() in a python script? Perhaps it would be possible to
> provide a
> > warning instead, and give an output that can be captured, like NA for the
> > coefficient estimates, instead of breaking of the function?
>
> Instead of grass.run_command(), you can use
>
> ps = grass.start_command()
> returncode = ps.wait()
>
> returncode is zero if the module finished successfully, non-zero if an
> error occurred, easy to capture in a script.
>

OK, thanks


>
> Markus M
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/grass-dev/attachments/20160323/e2d9a7a6/attachment.html>