[GRASS-user] [GRASSLIST:1148] Attribute editing

[Maciej Sieczka]

Joel Pitt napisa?(a):
> On 7/7/06, Maciek Sieczka <werchowyna at epf.pl> wrote:
>> You can't edit a category number. You can only edit attributes (besides
>> the key column, usually and by default called "cat"). Category is a
>> unique vector feature ID - if you could edit it, you would loose
>> connection between the vactor feature and it's attributes in table.
>> Read: http://grass.itc.it/grass61/manuals/html61_user/vectorintro.html
> 
> You can edit categories with v.category can't you?

Yes, but that's a different thing than Hardeep asked, I think.

> Although it seems that only systematic changes, such as adding a value
> to all categories, or generating a new category index.
> 
> Does anyone know if all vector objects MUST have a unique category?

No.

> I have a shape file of US counties, and want to link it to a table of
> county information which have the FIPS code as a key. However, because
> counties are not all singular vector objects some have more than one
> category.

Do you mean that one county happens to be represented by more than 1
areas (polygons)?

> I could link the county information directly to the category numbers.
> But this would end having lots of duplicate entries where the FIPS
> code of entries is the same but with different category numbers.

You can have one category for many objects. Then each object will have
all the attributes in a table that are assigned to that category.

> Ideally I'd like to be able to use the FIPS code

What's FIPS?

> as the category
> number - but if category number must unique then I have to go with
> duplicate entries.

Maciek