[GRASS-user] v.patch and keeping the attributes

[Mira Kattwinkel]

Thanks a lot!

I just did not interpret the paragraph  "When using the /-a/ flag..." 
correctly.

Maybe a note in the manual that v.patch takes care of the cats etc. 
would be helpful.

Mira


On 29/10/18 20:35, Markus Metz wrote:
>
>
> On Mon, Oct 29, 2018 at 6:13 PM Mira Kattwinkel 
> <kattwinkel-mira at uni-landau.de <mailto:kattwinkel-mira at uni-landau.de>> 
> wrote:
> >
> > Dear list,
> >
> > I would like to patch two vector maps together and keep their attributes
> > (with the same columns but not in identical order) using v.patch with
> > flag -e.
>
> Granted that the two vector maps have attributes in layer 1 which you 
> want to keep, you can use v.patch -e directly. v.patch will change 
> category values of all but the first map such that no conflicts with 
> identical categories from different input maps arise. There is no need 
> to prepare the input maps with v.category.
>
> v.patch takes care of different column ordering.
>
> HTH,
>
> Markus M
>
> >
> > Both maps have cats starting with 1. Hence, I thought I use v.category,
> > option 'add' to add a fixed (large enough value) to the categories and
> > creating a second layer to keep the attribute values like this:
> > v.category input=map1 layer=2 type=line output=map1_cat option=add
> > cat=100001
> >
> > Then I add a table to layer 2 with a column for the old cat:
> > v.db.addtable map=map1_cat layer=2 columns="cat_lyr1 integer"
> >
> > Next, I fill this column (I want to use this column to be able to later
> > join the attributes from the original maps):
> > v.to.db map=map1_cat layer=2 type=line option=query columns=cat_lyr1
> > query_column=cat
> >
> > Finally, I would like to use v.patch with flag e. However, this works
> > only for the table in layer 1. Hence, I wanted to use v.categroy to
> > change the layer numbers:
> > v.category input=map1_cat layer=2,1 type=line output=map1_cat2
> > option=chlayer
> >
> > And get the warning: WARNING: Database connection and attribute tables
> > for concerned layers are not changed
> >
> > I tried to first drop the table in layer 1 with:
> > v.db.droptable -f map=map1_cat
> > and then use v.category but that results in the same warning as before.
> > Layer 2 is still layer 2.
> >
> > Can anybody please explain to me what is wrong? I am still struggling to
> > get my head around categories and layers but I thought I found a way to
> > do it correctly.
> >
> > Thanks a lot,
> > Mira
> >
> >
> > --
> > Dr. Mira Kattwinkel
> > Quantitative Landscape Ecology
> > Institute for Environmental Sciences
> > University of Koblenz-Landau
> > Fortstraße 7
> > 76829 Landau
> > Germany
> > Phone: + 49 6341 280-31553
> > Office: Building I, Room 2.02
> >
> > _______________________________________________
> > grass-user mailing list
> > grass-user at lists.osgeo.org <mailto:grass-user at lists.osgeo.org>
> > https://lists.osgeo.org/mailman/listinfo/grass-user

-- 
Dr. Mira Kattwinkel
Quantitative Landscape Ecology
Institute for Environmental Sciences
University of Koblenz-Landau
Fortstraße 7
76829 Landau
Germany
Phone: + 49 6341 280-31553
Office: Building I, Room 2.02

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