[GRASS-user] r.cross doesn't work correctly.

[Gra]

ok thanks
but in my case the combination existed (there was not a null value
problem), the command skipped the first combination (category 1 with
category 1).

Grazia

2018-02-26 18:42 GMT+01:00 Markus Metz <markus.metz.giswork at gmail.com>:

>
>
> On Mon, Feb 26, 2018 at 2:38 PM, Markus Metz <
> markus.metz.giswork at gmail.com> wrote:
> >
> >
> >
> > On Mon, Feb 26, 2018 at 1:31 PM, Nikos Alexandris <
> nik at nikosalexandris.net> wrote:
> > >
> > > * Markus Metz <markus.metz.giswork at gmail.com> [2018-02-26 13:01:35
> +0100]:
> > >
> > >> On Mon, Feb 26, 2018 at 11:19 AM, Gra <graziaz at gmail.com> wrote:
> > >>>
> > >>>
> > >>> Dear community
> > >>>
> > >>> I use r.cross to combine and then reclassify a set of indicators.
> > >>>
> > >>> I realised that r.cross doesn't work correctly.
> > >>>
> > >>> I have two inputs maps with values from 1 to 3 each.
> > >>>
> > >>>
> > >>> the problem is that r.category doesn't list the first combination
> (eg 1
> > >>
> > >> to 1)
> > >>>
> > >>>
> > >>> eg
> > >>> r.category map=myinput at in_data
> > >>
> > >>
> > >>> 0
> > >>> 1 category 1; category 2
> > >>> 2 category 1; category 3
> > >>> 3 category 2; category 1
> > >>> 4 category 2; category 2
> > >>> 5 category 2; category 3
> > >>> 6 category 3; category 1
> > >>> 7 category 3; category 2
> > >>> 8 category 3; category 3
> > >>>
> > >>> in reality the first combination exists (0 is empty but  I should
> have
> > >>
> > >> there category 1; category 1)
> > >>>
> > >>> the problem is that I have to iterate on 700 cases and I wont check
> and
> > >>
> > >> correct manually.
> > >>>
> > >>>
> > >>> could  you fix it?
> > >>
> > >>
> > >> Please try trunk r72281
> > >
> > >
> > > Works for me, thank you.
> > >
> > >
> > > What about the -z flag, though?
> > >
> > > The manual reads:
> > >
> > > With the -z flag zero data values are not crossed. This means that if a
> > > zero category value occurs in any input data layer, the combination is
> > > assigned to category zero in the resulting map layer, even if other
> data
> > > layers contain non-zero data. In the example given above, use of the -z
> > > option would cause 3 categories to be generated instead of 5.
> >
> > The -z flag does not behave as explained in the manual. It comes from
> the old days when there was no NULL encoding in GRASS, and zero was used as
> nodata. Now the -z flag means that with the -z flag, NULL values are not
> crossed, not that zero data are not crossed. This has been introduced in
> 2013 with r55276. The results of r.cross without the -z flag might look
> strange if any of the input maps contains NULL cells.
>
> The manual has been updated in r72285 to explain the current (as of
> r55276) behaviour with regard to the -z flag. Additionally, NULL values get
> now the label "NULL".
>
> Markus M
>
> > >
> > > By the way, it should be: "In the following example..." and not "In the
> > > example given above...".
> > >
> > > Nikos
> > >
> > >
> > >> Markus M
> > >>
> > >>> thanks
> > >>> Grazia
> >
>
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