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

[Moritz Lennert]

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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