[GRASS-user] Re: [GRASSLIST:1140] Re: Qn. on extracting from multiple rasters, data corresponding to vector polygons

Vishal Mehta vishalm1975 at gmail.com
Fri Sep 15 01:50:38 EDT 2006

Hi all,
I had, with your help, added 500 columns of rain data from 500 corresponding
rasters, t0 my vector map of 8 watersheds.

Now i want to add another 500 columns to the same vector map, but from
different 100 rasters, namely derived reference ET maps i have created.

My qna are:
1. Should i use the same table but first connect to a different empty
'layer' first using v.db.connect?

2. If i do the above, will i be able to extract individual layers of the
table in openoffice calc or Excel?

3. i was going to just copy my vector map and then delete the original 500
rain columns from the table, and then add the 500 ET columns- but i was not
able to do it. i tried commands like
 echo "DELETE COLUMN 'Rain1' FROM watershed8c" | db.execute

echo "DELETE FROM watershed8c COLUMN LIKE 'rain'" | db.execute
but they did'nt work.

How do i delete say all columns that start with the text 'rain' from a

thanks much,

On 6/28/06, Hamish <hamish_nospam at yahoo.com> wrote:
> Vishal Mehta wrote:
> > 2. My rasters are large, covering south asia (60E-100E, 5N-45N; 0.5
> > degree resolution). My vectors are very small (covering small part of
> > south-west India). Perhaps this effects the processing time..should i
> > mask the rasters and then do the adding of columns?
> add in a step after MASK creation:
> g.region zoom=MASK res=0.5 -a
> leave out the g.mlist sep=space, it uses the whole word!
> `g.mlist pat='*'` is enough.
> Hamish
> ps - new mailing list address: grassuser at grass.itc.it
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