Am 17.05.2011 um 16:14 schrieb Moritz Lennert:
On 16/05/11 16:32, Johannes Radinger wrote:
Hallo,
I've got a point file and populated (v.what.rast) it with values
from a flow direction raster (flow direction from r.watershed).
I want to use these values to rotate the symbol in ps.map but
therefore I've to recalulcate the values in the direction-column
of the point file (x*45+90 or so).
How can that be done? I thought about v.reclass but don't really
know how?!
Another option would be to access the sqlite database and perform
the calculation there (I am working in a python script) like:
database = sqlite3.connect(os.path.join(gisdbase, location,
mapset, 'sqlite.db'))
db = database.cursor()
db.execute .... but what is the correct command for calculation
within a database??
Probably it is easier than I think... :)
If you want to modify an existing column:
v.db.update col=YourExistingColumn value=YourCalculation
If you want to create a new column:
v.db.addcolumn col="YourNewCol double precision"
v.db.update col=YourNewCol value=YourCalculation
Thank you that was what I was looking for...
/j
Moritz
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