[GRASS-user] v.to.rast with text column

[Dylan Beaudette]

On Wednesday 14 October 2009, Dylan Beaudette wrote:
> Great! Thanks for the tips. I was able to accomplish this (in PostGresql)
> with the following steps:
>
> 1. generate unique list of text categories as a temp table
> 2. add a serial column to the temp table (auto-incrementing integer)
> 3. add new column to original table
> 4. UPDATE original table with the new serial number, assigned by text
> category 5. v.to.rast
>
> Cheers,
> Dylan

One small note-- I noticed that the operation takes MUCH longer to complete 
when the labelcolumn argument is specified. So long in fact, that I canceled 
the process, and converted only the integer representation to raster. I then 
added the category labels with r.category. Something in v.to.rast was causing 
the postgresql instance to peg the CPU at 100% when specifying a labelcolumn. 
This was for a rather large vector conversion, about 410520 features.

Cheers,
Dylan


> On Wednesday 14 October 2009, Markus Neteler wrote:
> > IMHO ticket 175 has been fixed. I can now run (thanks to Martin):
> >
> > v.db.select lsat7_training
> > cat|name|id
> > 1|water|1
> > 3|forest|2
> > 4|forest|2
> > 5|asphalt|3
> > 6|asphalt|3
> > 7|water|1
> > ...
> > v.to.rast in=lsat7_training out=lsat7_training use=attr col=id
> > labelcol=name
> >
> > As Achim says: col must be numerical and should be the numerical
> > representation of the text attributes (see example above).
> >
> > Markus
> >
> > On Wed, Oct 14, 2009 at 1:39 PM, Hamish <hamish_b at yahoo.com> wrote:
> > > see also  https://trac.osgeo.org/grass/ticket/175
> > >
> > > Achim wrote:
> > >> v.to.rast has the option:
> > >>
> > >> --%<--
> > >> labelcolumn=name
> > >>     Name of column used as raster category
> > >> labels
> > >> --%<--
> > >>
> > >> And the raster values have to be numeric:
> > >>
> > >> --%<--
> > >> column=name
> > >>     Name of column for attr parameter (data type
> > >> must be numeric)
> > >> --%<--
> > >>
> > >> (http://grass.itc.it/grass64/manuals/html64_user/v.to.rast.html)
> > >>
> > >> Try to make unique numbers from your string-column and
> > >> convert them with
> > >> column=... and labelcolumn...
> > >>
> > >> Achim
> > >>
> > >> Dylan Beaudette schrieb:
> > >> > Hi,
> > >> >
> > >> > v.to.rast is letting me know that it does not accept
> > >>
> > >> text columns in an
> > >>
> > >> > attribute table. Has anyone figured out a simple
> > >>
> > >> approach to making this
> > >>
> > >> > work? I suppose that I could import the data into R,
> > >>
> > >> convert to factors, save
> > >>
> > >> > the levels back to the table and use those... but
> > >>
> > >> there may be something out
> > >>
> > >> > there that is simpler and can be done within GRASS.
> > >>
> > >> Also, would this be
> > >>
> > >> > something worth adding to the v.to.rast code?
> > >> >
> > >> > Cheers,
> > >> > Dylan
> > >
> > > _______________________________________________
> > > grass-user mailing list
> > > grass-user at lists.osgeo.org
> > > http://lists.osgeo.org/mailman/listinfo/grass-user



-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341