[GRASS-user] update cat column in vector data set

[Stefan Luedtke]

Thanks, that did the trick.  

I guess, in order to get a consecutive "cat", I do have to reclass
(v.reclass) the vector- or is there any shortcut?

Sorry for the noise, but vector stuff  in grass is still a bit confusing
to me.

Cheers, 

Stefan

On Fri, 2012-08-17 at 11:38 +0200, Moritz Lennert wrote: 

> On 16/08/12 20:23, Stefan Luedtke wrote:
> > That helped for my general understanding, thanks a lot, but I can not
> > figure out how.
> >
> > Can anyone just give a few hints on the procedure, basically, how to
> > continue after "v.clean", please?
> 
> You could try using v.extract with something list list=1-9999 in order 
> to create a new vector file which contains only those polygons (and 
> their attributes in the table) which exist in your cleaned file.
> 
> Moritz
> 
> >
> > Cheers,
> >
> > Stefan
> >
> > On Thu, 2012-08-16 at 16:29 +0200, Markus Metz wrote:
> >> On Thu, Aug 16, 2012 at 1:10 PM, Stefan Luedtke<sluedtke at gfz-potsdam.de  <mailto:sluedtke at gfz-potsdam.de>>  wrote:
> >> >  Dear friends,
> >> >
> >> >  I am struggling with the following point.
> >> >
> >> >  I have created a shape of subbasins based on a raster data set. Since this
> >> >  yields some tiny (pixel size) areas, I run"v.clean"  with a certain
> >> >  threshold to remove/append those artifacts. However, the resulting vector
> >> >  data set still holds all categories of the old one, even so, some areas have
> >> >  been removed.
> >>
> >> This is because several areas can belong to the same category, e.g.
> >> basin id, and the category of a deleted area may still be used by
> >> another, existing area. BTW, it is not uncommon that one raster basin
> >> is represented by several vector areas.
> >> >
> >> >  So my question: How can I update these values that the number of categories
> >> >  matches the number of areas?
> >>
> >> You can delete the table and create a new table. Otherwise, entries in
> >> the attribute table that are no longer used do not do harm.
> >>
> >> HTH,
> >>
> >> Markus M
> >>
> >> >
> >> >  I tried v.category (but der is not update function).
> >> >
> >> >  Cheers,
> >> >
> >> >  Stefan
> >> >
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> >> >
> >
> >
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> 
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