[GRASS-user] Learning to use vector layers

Jaime Carrera jaicarrerahdez at yahoo.com
Mon Mar 26 10:03:49 EDT 2007


Hi Daniel,

You could also generate a table like this:

id|easting|northing|9001|9002|9003|...|9012|9101|...

Then you have your data in one table which can be
linked to the vector file. Such a table can be
generated from other tables using SQL commands.

HTH

Jaime


--- Daniel Victoria <daniel.victoria at gmail.com>
escribió:

> Hi all,
> 
> I have a vector problem and I think it might be a
> job for vector layers.
> I have a postgresql table with daily meteorological
> station data (~10
> years, 300 stations) and I'd like to get average
> monthly precipitation
> for each station.
> That I can easily do with a SQL query, generating a
> view and attaching
> the view to a vector file where the CAT column is
> the station number.
> The problem is, I can only attach one SQL view at a
> time since the
> vector file has only one category (from what I read,
> it's one category
> per layer connection correct?)
> 
> So, I though about some options:
> 1) either generate 1 vector file for each month -
> simple but then I
> don't learn about layers
> 2) keep changing the database connection for each
> month - works but
> seems kind of improvisation
> 3) Use layers, one layer for each month. I'd have
> the advantage of not
> having categories for stations with no data for a
> specific month for
> example and also, I'd learn about layers
> 
> So, the proper questions:
> Does this sounds like a job for vector layers?
> How do I add categories to a vector file but, the
> categories should
> come from a column in a SQL view? From what I read,
> v.category can
> only add sequential cats and I'd like the cats to be
> the station
> number.
> 
> Cheers and sorry for the long email
> Daniel
> 
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