[GRASS-user] v.extract and layer/table settings with layer=2

[Johannes Radinger]

Hi all,

this is maybe I quite easy routine for somebody that is using v.extract
regularly.

Here my challenge: I have a vector map (initially created by v.net tools)
that has several layers and associated tables to each layer. Now for
further processing I want to extract only some features from layer=2 and
the corresponding attribute table.

I can do that using "v.extract input=mymap1 layer=2 where='mycol=x'
output=mymap2". The resulting 'mymap2' has an attribute table connected to
layer 2 and there are no other layers (e.g. there is no layer 1, which is
considered in most grass tools as default layer). So I wanted to change
that and to shift layer 2 (and the attribute table) to layer 1 using
"v.category option=chlayer layer='2,1' input=mymap2 output=mymap3"

...however, this does not change the attribute table connection (as checked
by "v.db.connect -p "). So I guess I also have to use v.db.connect in some
way (??) to get the attribute table shifted from connection at former layer
2 to layer 1 (unused).

In my opinion this is quite a bit complicated, considering that I just
wanted to extract some features from a 3-layered map?? Is there a easier
way or a general description if one want to extract some feature that are
not stored in layer 1?

All the best,
Johannes
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