[GRASSLIST:3794] Re: Vector Manipulation

[Christoph Simon]

On Thu, 30 May 2002 09:24:25 +0200
Radim Blazek <blazek at itc.it> wrote:

> On Wednesday 29 May 2002 09:57 pm, Christoph Simon wrote:
> > Hi!
> >
> > I just joined this list. I was wondering if there is any grass tool
> > like r.mapcalc for vector data. In particular, I would need a way to
> > do two things: one is to join several adjacent area polygons into one
> > bigger. I found an add-on tool called v.rmedge which does exactly the
> > inverse of what I'm trying to do. 
> 
> v.reclass -d 
> (warning: area labels may be incorrect some times - you can get
> more labels in one area - no problem because they are of the same
> category; i'm not sure but i worry that you can get even not labeled
> areas - problem)

Thanks, as far as I tested this, it seems to do just what I
wanted. Didn't run into any label problems (yet). Just one dought: As
I understood, a reclassified raster layer is just that, a
reclassification, depending on the original layer. Is this also the
case with vector layers? From the file sizes, it seems that these are
independent maps.

> > And the other one is to select or
> > deselect certain lines in a resulting map C depending on their
> > presence in map A and/or B (with or without a snapdistance).
> 
> I would use:
> v.to.rast  (A,B,C)
> r.report or r.mapcalc (or something)
> v.reclass or v.extract (based on results of r.* modules)

Hm. Not sure to have understood this: You mean, I should use the
raster maps as a mask?

Thanks again.

-- 
Christoph Simon
ciccio at kiosknet.com.br
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