[GRASS-user] Nothing Inserted into Attribute Table from v.to.db

[Moritz Lennert]

On 03/10/08 08:57, Ryan R. Rosario wrote:
> I have vector maps called "incidents" (points) and "roads" (lines). For some
> reason, I am getting nothing as output in the final attribute table; 

First of all: could you state clearly and precisely what you want to do ?

> that
> is, the attribute table is not being updated at all. I am sure I am making
> some silly mistake.
> 
[...]
> What could I be doing wrong?

This:
 > v.distance from=incidents to=roads output=connecting_lines upload=cat
 > column=nearest
 > #I copied table "incidents" to "connecting_lines" and called it
 > "connecting_lines". I used the option
 > #key=nearest.

(Second: please be more explicit in the description of your actions. In 
this case, for example, please tell us which command you used. I assume 
v.db.connect...)

The output map of the v.distance command contains only lines for 
visualisation which do not even contain a category value allowing to 
identify each line. You cannot, therefore, link the map to a table. 
Well, you can, but no records in the table will correspond to a line as 
the latter do not have a ids.

Debatedly, v.distance could be enhanced to include some information in 
an attribute table accompanying the map, such as from_cat and to_cat, 
but someone would have to implement that.

Moritz