Ciao Madi,
You could use db.execute and do something like:
db.execute sql="ALTER TABLE vectormap ADD COLUMN reclass_column TEXT;
UPDATE vectormap SET reclass_column = CASE
WHEN old_column = ' old value 1' THEN ' new value 1'
WHEN old_column = ' old value 2' THEN ' new value 2'
WHEN old_column = ' old value 3' THEN ' new value 3'
ELSE ' new value 4'
END; "
Maybe worth adding as an (validated) example to the manual of db.execute
(https://grass.osgeo.org/grass78/manuals/db.execute.html)…
Cheers
Stefan
P.S.: I did not alidate the SQL syntax, but it should be roughly along those
lines…
From: grass-user <[email protected]> On Behalf Of Margherita
Di Leo
Sent: onsdag 17. juni 2020 10:35
To: GRASS user list <[email protected]>
Subject: [GRASS-user] Reclassify a vector adding a column
Hi,
I need to reclassify a vector in the following way: based on a column of type
string I have to create a new column of type string based on certain rules that
I give upon the first column, and I thought it would be really handy if I could
do it like CASE WHEN... THEN ...
I have tried to feed a similar rules file to v.reclass but this statement is
not recognised. How can I translate it? Furthermore, I would like to be able to
just add a reclass column rather than creating a new vector file, is that
possible? How?
Thank you in advance
Kind regards,
--
Margherita Di Leo
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