[GRASS-user] append data after a v.in.ascii import

[Markus Metz]

On Sat, Oct 27, 2018 at 10:00 AM Frank David <frank.david at geophom.fr> wrote:
>
>
> Le 26/10/2018 à 21:11, Markus Metz a écrit :
>
>
>
> On Fri, Oct 26, 2018 at 7:17 PM Frank David <frank.david at geophom.fr>
wrote:
>
> > If you want to preserve attribute values, use v.patch -e, otherwise
don't use the -e flag, but then you might get duplicate category values.
>
> >  v.patch -c should not work because -c is not a recognised flag. Which
GRASS version did you use with v.patch -c?
>
> I'm sorry, when I wrote -c it was -e of course ! I'm using Grass 7.4.1
>
> But even with -e, as I wrote, the cat of the second file is shift by
one... (?)

This is correct because it is needed to preserve attributes.
>
> I have used -e because I need to add my attribute table from both file.
But I had imagine to keep cat relation with data, but it's may be better to
add a id field ? is there any way to increment a unique key automatically
when data are appended ?

This unique key is automatically incremented when data are appended and
attribute values need to be preserved. The unique key (more generally: the
object identifier that determines to which category an object belongs) is
the category value.

I am sure the output with shifted category values is exactly the output you
want when preserving attribute values.

Markus M

>
> Frank
>
>
> Markus M
> >
> > Frank
> >
> > Le 26/10/2018 à 18:44, Markus Metz a écrit :
> >
> >
> >
> > On Fri, Oct 26, 2018 at 2:26 PM Frank David <frank.david at geophom.fr>
wrote:
> > >
> > > I reply to myself,
> > >
> > > I mistook, if I append, I see a cat shift too. The fisrt cat of the
> > > second map is shift by one. It's strange no ?
> >
> > Suppose there is a feature with cat 1 in map A and a feature also with
cat 1 in map B, but corresponding attribute values for cat 1 are different
between map A and map B. In order to avoid such conflicts, v.patch shifts
category values and updates the resultant attribute table accordingly, such
that attributes for each feature are preserved.
> >
> > Markus M
> > >
> > > Frank
> > >
> > > Le 26/10/2018 à 14:17, Frank David a écrit :
> > >
> > > > Hi Stephan,
> > > >
> > > > If I add two vector in a new one with :
> > > >
> > > > v.patch -c input=map1,map2 out=map3
> > > >
> > > > I notice the map3 first cat start at 2 instead of 1, so all cat are
> > > > shifted by one. Do you have an idea of the reason ?
> > > >
> > > > If I append my map1 with map2 :
> > > >
> > > > v.patch -c -a input=map2 output=map1 --overwrite it works well
> > > >
> > > > Thank you
> > > >
> > > > Frank
> > > >
> > > > Le 26/10/2018 à 12:01, Stefan Blumentrath a écrit :
> > > >> Hi,
> > > >>
> > > >> Try:
> > > >> v.patch -a
> > > >> https://grass.osgeo.org/grass76/manuals/v.patch.html
> > > >>
> > > >> (assuming attribute tables are equal).
> > > >>
> > > >> Cheers
> > > >> Stefan
> > > >>
> > > >> -----Original Message-----
> > > >> From: grass-user<grass-user-bounces at lists.osgeo.org>  On Behalf Of
Frank David
> > > >> Sent: fredag 26. oktober 2018 11:39
> > > >> To:grass-user at lists.osgeo.org
> > > >> Subject: [GRASS-user] append data after a v.in.ascii import
> > > >>
> > > >> Hello,
> > > >>
> > > >> I wonder what is the best way to append a vector map and his
attribute data created with v.in.ascii  ?
> > > >>
> > > >> Thanks
> > > >>
> > > >> Frank
> > > >>
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> > > >
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