[GRASS-user] v.select - so close but so far!

[M S]

thanks Hamish!  i got it, finally.  chalk one up to user error.  thanks for
your trouble shooting help, it did the trick!

my centroid was outside the polygon, so i put it inside, and built
topology.  then i used the type=area for binput, and worked great!
extracted points and lines and should be good to go.



On 6/22/06, M S <mseibel at gmail.com> wrote:
>
> i not doing anything advanced, at least it shouldnt be.   i have a county
> wide, line roads dataset and county wide building points dataset.  all i
> want to do is clip both vectors back to the same extent. basically i just
> want the features either clipped to the boundary of a polygon i built, or
> even just select overlapping ones, and write them to a new file.
>
> i may be missing the concept of this, "features need a category number in
> order to be extracted. does d.what.vect show cat numbers for your points?"
>
> d.what.vect shows catagory numbers for the building points.  I'm not sure
> i understand what the category has to do with v.select.
>
> v.info clipper does show boundaries and centroids and area (and
> islands?!?)   i recently modified the clipper polygon box, and it seems that
> the centroid is outside the box now.  i'll put it in and give it another
> whirl.
>
> thanks for the help!
>
>
> On 6/22/06, Hamish <hamish_nospam at yahoo.com> wrote:
> >
> > > i'm using v.select as such:
> > >
> > > v.select ainput=buildings atype=point alayer=1 binput=clipper
> > > btype=area blayer=1 outpout=buildclip operator=overlap
> > >
> > > where buildings are a point, with layer 1 (verified through QGIS)
> > > where clipper is a polygon that is the bounds i want to pull the
> > > building points from.  the odd thing about this dataset, is that when
> > > i go to load in QGIS, there are two layer options, layer 0 which is
> > > polygon and layer 1 which is line.
> > >
> > > i cant specify blayer=0 in this function or it says must be 1 or
> > > greater.
> > >
> > > is there a way to put the polygon layer on layer 1? i can only think
> > > this might be why there's a problem.  I still dont really grasp the
> > > layers concept very well.  i understand it has to do with linking
> > > features to a database, but why does it put different features on
> > > different layers?
> > >
> > > the output i get is a file with no data in it.
> >
> >
> > I don't think QGIS layers == GRASS layers.
> >
> > Unless you are doing something advanced, usually grass vector layer is 1
> >
> > and you can forget about that.
> >
> > "v.info clipper"  show boundaries + centroids or lines?
> >
> > features need a category number in order to be extracted. does
> > d.what.vect show cat numbers for your points?
> >
> > v.select works well and should be pretty simple, so don't give up.
> >
> >
> > Hamish
> >
>
>
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