[GRASSLIST:9311] Re: Extracting and sum values in a tab

[Luca Casagrande]

Alle 19:00, lunedì 05 dicembre 2005, hai scritto:
> On Mon, 5 Dec 2005 19:43:41 +0000
>
> Luca Casagrande <luca.casagrande at gmail.com> wrote:
> > Hi guys
> >
> > I have got an area vector layer that describes the extension of different
> > cities and also the region in where them are; the table associated is
> > something like this:
> >
> > REGION		CITY		EXTENSION
> >     A			test1			100000
> >     A			test2			5000
> >     B			........			20000
> >     C                 ........			300000
> >
> > I'd like to create a surface layer that describes the extensionof each
> > region and with a tab like this one:
> >
> > REGION			TOTAL POPULATION
> > 	A				Sum of all
> > 	B				Sum of all
> > 	C				Sum of all
> >
> > Can this be done?
> >
> > Thx
> > Luca
>
> I'm not sure I understand your question because it is unclear to me
> what you mean by extension.
>
> If you wanted to overlay the different layers and add values in areas
> of overlap, one way to do that would be to convert the vectors to
> rasters and use r.mapcalc.
>
> T

The first step would be to join areas, in the same vector layer, who have got 
the same attribute on the tab (in my example the same region). Then i'll sum 
the total population on each region.

Thx for all!