[GRASS-user] Select specific layer when copying vector map
mlennert at club.worldonline.be
Tue Aug 9 05:23:10 PDT 2016
On 09/08/16 13:48, Johannes Radinger wrote:
> I'd like to create from an existing GRASS vector map that has 3 layers
> (with three attribute tables) a new vector map that has only one
> layer and its associated attribute table (here the information related
> to layer 3).
> What I am doing so far (in python):
> # First copy the map to a new one and copy table (that of layer 3)
> # that I want to re-connect to new map
> # Second delete all tables of the newmap
> for i in [1,2,3]:
> # Third reconnect a table to the newmap
> When I check in the attribute table manager, there is only one layer
> listed (layer 1).
> Similarly, v.db.connect reports:
> v.db.connect -p map=newmap
> Vector map <newmap> is connected by layer <1/table_layer3_copy> table
> <table_layer3_copy> in database [...]
> However, in d.vect I can still select from all three layers that were in
> the old map (-1,1,2,3),
> and all of them can be displayed (with -1 specified)?
> So does may newmap have three layers or only one?
3. Layers are defined by category values, not by attribute tables.
> How can I make the third layer the default layer 1 and remove all other
> Or is there a way to copy a vector map with just a single layer and its
> associated table specified as default?
Try v.extract instead of g.copy.
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