Hi Vero,
as I understand it, vector files in GRASS need a key column if they have
an attribute table. But I don't see that this has to be a column named
'cat'. However, GRASS is quite inconsistent here. Some functions ensure
the existence of a 'cat' column, such as v.db.dropcolumn (just gives an
error if you try to remove the 'cat' column), whereas other functions
let one define other columns as key column (e.g. manually in the GUI or
v.db.addtable).
The latter happened with my vector map, i.e. a different column was
defined as key column. Therefore it is confusing why
rgrass7::writeVECT() just adds the cat column and without any
notification. This makes no sense to me and is annoying as my subsequent
workflow produced unexpected results and I had to trace back the error
which took a while.
From my perspective as user it would be great if a more consistent
solution regarding the treatment of key columns could be found, i.e.
either always ensure the existence of a column named 'cat' or just
accept if the user specifies a different key column.
Regards,
Tobias
Am 20.10.21 um 20:41 schrieb Veronica Andreo:
Hello Tobias,
The cat colum is the ID that GRASS uses for vectors, hence this is expected
and right. The same happens if you import a gpgk or shape or any other
vector file into GRASS. See
https://grass.osgeo.org/grass78/manuals/vectorintro.html for further info
HTH,
Vero
El mié, 20 oct 2021 a las 9:34, Tobias Pilz (<[email protected]>)
escribió:
Dear list,
when I use in R the writeVECT() command the resulting map in GRASS got
the 'cat' column silently added to its attribute table if it didn't exist.
The vector object in question was previously imported to R via
readVECT() and had a different column defined as key column.
Is this behaviour of writeVECT() intentional? If yes, why so and
wouldn't it make sense to give a warning?
Note: I used rgrass7 version 0.2-6 together with GRASS 7.8.5 under Linux
(opensuse).
Regards,
Tobias
_______________________________________________
grass-stats mailing list
[email protected]
https://lists.osgeo.org/mailman/listinfo/grass-stats
--
Dr. Tobias Pilz
Climate Resilience - Research Department 2
Tel: +49 331 288 2539
E-mail: [email protected]
Potsdam Institute for Climate Impact Research
Telegraphenberg A 31
P.O. Box 60 12 03
D-14412 Potsdam
www.pik-potsdam.de/members/topilz
You are welcome to send me PGP/GnuPG encrypted messages. Please find my public
key on the common servers.
_______________________________________________
grass-stats mailing list
[email protected]
https://lists.osgeo.org/mailman/listinfo/grass-stats
