[GRASSLIST:9309] Re: Extracting and sum values in a tab

[Trevor Wiens]

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
-- 
Trevor Wiens 
twiens at interbaun.com

The significant problems that we face cannot be solved at the same 
level of thinking we were at when we created them. 
(Albert Einstein)