[GRASSLIST:10024] Re: Problem using v.to.db - option cat

[wqual]

Hi Radim,
thank you very much for your reply. I tried to apply this to another issue - a 
polygon buffer theme with a donut polygon [1]. However, the solution 
described by you also creates another centroid within the "hole" of the 
polygon. Any ideas?

Best regards,

Wolfgang

[1]  http://grass.itc.it/pipermail/grassuser/2006-January/032130.html

--8<------------------------------------------------------------------------------------------------
Am Mittwoch 25 Januar 2006 pH:23:11 vormittags schrieb Radim Blazek:
> On 1/24/06, René Capell <rene.ca at web.de> wrote:
> > Hi Wolfgang,
> >
> > actually I am a little bit confused, because i thought categories MUST
> > be unique (I=beginner), but if I understood your problem right,
> > v.category should do it:
> >
> > v.category in=stream option=del
> > v.category in=stream option=add step=1
>
> Categories does not have to be unique. More elements in map can be linked
> to single database row. This is similar to multi* features in simple
> features.
>
> In this particular cas the category in streams probably have some meaning.
> Suggested v.category del/add will work but the information is lost.
> If you want a single row for each line you can assign new cats in a new
> layer v.category in=stream output=stream2 layer=2
> and create and connect 2 tables:
>   echo "create table stream2_1 (cat int)" | db.execute
>   echo "create table stream2 _2 (cat int, cat_orig int)" | db.execute
>   db.connect map=stream2 layer=1 table=stream2_1
>   db.connect map=stream2 layer=2 table=stream2_2
>   v.to.db map=stream2 layer=1 option=cat
>   v.to.db map=stream2 layer=2 option=cat
> and upload original categories to stream2 _2
>   v.to.db map=stream2 qlayer=1 layer=2 option=query qcol=cat col=cat_orig
>
> Now you have in the layer 2 unique categories and values of original
> categories are uploaded to the attribute table of layer 2.
>
> Radim
>
> > Greets, Rene
> >
> > >Hi list,
> > >I tried to assign unique cat-values to a vector (copy of
> > > streams at PERMANENT, spearfish dataset)file using v.to.db. I expected
> > > each row to get a unique cat-value (1,2,3 ...), but received a
> > > different result: in total I have three different values for cat (1,2
> > > and 3 like 1,1,1,2,2,2,2,2,3,3,2,2,2,1). How can I assign unique
> > > cat-values?
> > >
> > >Greetings,
> > >
> > >Wolfgang