v.stats.rast for category raster or vector cross statistics

Dear lists,

Given Av (vector of polygons) and Br (raster of a categorical variable,
i.e. a classification or a soil map) I want to calculate
for each polygon in Av, the surface of each category from Br.

v.stats.rast almost does it, but calculates lumped stats for each
polygon (i.e, assumes that Br is a continuous variable).

Alternatively, I could have Br as another vector Bv, but don't find
the way of calculating cross stats as r.stats -a in=Ar,Br would do for
raster layers.

Converting Av into raster Ar is inconvenient, as the polygons are few
and small and would have to use a very samll cell size (Br is large)

Any easier way through R?

--
Dr. Agustin Lobo
Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
LLuis Sole Sabaris s/n
08028 Barcelona
Spain
Tel. 34 934095410
Fax. 34 934110012
email: Agustin.Lobo at ija.csic.es
http://www.ija.csic.es/gt/obster

Agustin,


I would suggest taking a look at starspan
(http://starspan.casil.ucdavis.edu/). It specializes in
vector-on-raster analyses and has a --count-by-class flag for
categorical rasters. I wrote a bit more about it at
http://www.perrygeo.net/wordpress/?p=30 .

- matt
On 10/22/07, Agustin Lobo <Agustin.Lobo at ija.csic.es> wrote:

Dear lists,

Given Av (vector of polygons) and Br (raster of a categorical variable,
i.e. a classification or a soil map) I want to calculate
for each polygon in Av, the surface of each category from Br.

v.stats.rast almost does it, but calculates lumped stats for each
polygon (i.e, assumes that Br is a continuous variable).

Alternatively, I could have Br as another vector Bv, but don't find
the way of calculating cross stats as r.stats -a in=Ar,Br would do for
raster layers.

Converting Av into raster Ar is inconvenient, as the polygons are few
and small and would have to use a very samll cell size (Br is large)

Any easier way through R?

--
Dr. Agustin Lobo
Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
LLuis Sole Sabaris s/n
08028 Barcelona
Spain
Tel. 34 934095410
Fax. 34 934110012
email: Agustin.Lobo at ija.csic.es
http://www.ija.csic.es/gt/obster