[GRASSLIST:9953] Re: R, kriging and grass6

[Roger Bivand]

On Mon, 23 Jan 2006, ivan marchesini wrote:

> Hi to all...
> we are triyng to use kriging using R and grass6,
> We have seen a lot of documentation about R and GRASS5 but not so many
> about grass6...
> the problem is that we are trying to do an interpolation using the
> functions gmeta6 and kriging...
> if we are not wrong, the R library GRASS is developed for grass5 and
> inside there is the function krige.G that use the location data acquired
> using the gmeta() function...
> the problem is that we have found the gmeta6() function but not the
> krige.G6 function and obvously the krige.G doesn't work using the
> location data of grass6 (obtained using gmeta6)  
> 
> how can we simply solve this problem....

krige.G was a nasty hack, and should best be forgotten. The direct route 
is to use the sp classes in R and implemented for GRASS in spgrass6 - see 
GRASS News for the GRASS side and R News for the R side, combined with a 
proper R geostats package. Of those available, gstat is tightly bound to 
sp classes, so as far as I know, the only bit that needs doing by hand is 
to create a GridTopology object, or a SpatialGrid object, from the data 
returned by gmeta6() to pass to the kriging prediction function.

If you like, we can iterate to a working example from passing the vector 
points to R from GRASS, doing the modelling and kriging predictions, and 
passing the prediction rasters back to GRASS, but I'd like input from 
users to make the description sound.

Best wishes,

Roger

> 
> thank you
> 
> Ivan
> 
> 
> 
> 

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no