[GRASS-user] Collapsing many layers into 1

[Martin Landa]

Hi,

2008/1/23, Neil Godfrey <neil at thegodfreys.net>:

> My problem is a little different.  I have just one map, but many layers.
> I want to get one map, with just one layer.

you can use `v.category chlayer=` to change layer number, but it will
not touch attribute data.

v.category in=map out=map_1 chlayer=2,1,3,1,4,1

You can also extract layers to single-layer vector maps and the to patch them.

for layer in `seq 2 10`; do
v.extract in=map out=map_${layer} layer=$layer where=cat>0;
done

v.patch in=`g.mlist vect pat=map_*` out=map_patch -e
v.clean ...

Martin

> On Tue, 2008-01-22 at 10:58 +0100, Martin Landa wrote:
> > Hi,
> >
> > 2008/1/22, Neil Godfrey <neil at thegodfreys.net>:
> > > The census 2000 administrative boundaries are shapefiles, where every
> > > county is a separate file.  So v.in.ogr creates a layer for every
> > > county.  So for example, I get 83 layers for the 83 counties in
> > > Michigan, which correspond to 83 tables, each with just one category.
> > >
> > > What I want is one layer with 83 categories.  I've had no luck with
> > > v.overlay, v.extract, v.patch, etc. because all those tools preserve the
> > > layers in the output map.
> > >
> > > Is there any way to do this?
> >
> > If the attribute tables have the same structure (number of columns,
> > data types and key column), you can patch maps using
> >
> > v.patch -e in=`g.mlist vect pat='con*' out=con_patch
> > v.clean in=con_patch out=con_clean tool=snap,break,rmdupl thresh=[value]
> >
> > ?
> >
> > Martin
> >
>
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-- 
Martin Landa <landa.martin at gmail.com> * http://gama.fsv.cvut.cz/~landa *