[GRASS-dev] [GRASS-user] r.series weights to zero

[Markus Metz]

On Fri, Jun 8, 2018 at 12:30 PM, Frank DAVID <frank.david at geophom.fr> wrote:
>
>
>
>
> Cordialement,
> Frank David
>
>
> -------- Message d'origine --------
> De : Markus Metz
> Date :07/06/2018 17:30 (GMT+01:00)
> À : Frank David
> Cc : grass-user , GRASS developers list
> Objet : Re: [GRASS-user] r.series weights to zero
>
>
>
> On Tue, Jun 5, 2018 at 2:51 PM, Frank David <frank.david at geophom.fr>
wrote:
> >
> > Hi all Grass users,
> >
> > It's seems that r.series weights does not accept zero as weight... Is
it possible ?
>
> Yes, weights must be positive.
>
> > and so, why ?
>
> A zero weight means that all values in this map are ignored. Zero weights
can also cause the sum of weights to be zero, leading to division by zero
and finally to +inf / -inf as a result
>
> Thank you Markus for your reply.
> I would think it would have been interesting to use zero as weight on
some raster in order to use (or not) them depending on the context. For my
purpose i will use a value next to zero.

Agreed. The underlying functions test if the sum of weights is zero, thus
it is ok if at least one weight is larger than zero, otherwise the result
is NULL. Zero weights are now allowed in r.series, trunk r72789.

Markus M

> Thanks again
> Frank
>
>
>
> Markus M
> >
> > I've got the following error message when running r.series with one
weight set to 0
> >
> > "/usr/local/grass-7.4.0svn/etc/python/grass/script/core.py",
> > line 332, in handle_errors
> >     returncode=returncode)
> > grass.exceptions.CalledModuleError: Module run None
> >
> > Thank you for your comment.
> >
> > Frank
> >
> >
> > _______________________________________________
> > grass-user mailing list
> > grass-user at lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/grass-user
>
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