[GRASSLIST:10529] Re: help with R and GRASS6

[Thomas.Adams at noaa.gov]

Carlos,

Thank you! That helps me as well. I got to the point following Roger's example using my own 
dataset, but:

OK_pred <- krige(IMMERSIONE~ 1,locations=giaciture,newdata=mask_SG,model=efitted)

returns a DataFrame, not a SpatialGridDataFrame! So, writeRast6sp() failed for me. I could 
use R's image() 
command to see the kriged surface in R, but had not seen how to get it into GRASS. 
Interestingly, my equivalent 
of the line:

cvgm <- variogram(IMMERSIONE~1,locations=giaciture,width=400,cutoff=4000)

would not work. I had to use:

cvgm <- variogram(giaciture$IMMERSIONE~1,locations=giaciture,width=400,cutoff=4000)

Regards,
Tom

----- Original Message -----
From: "Carlos \"Guâno\" Grohmann" <carlos.grohmann at gmail.com>
Date: Wednesday, February 22, 2006 5:00 pm
Subject: [GRASSLIST:10527] Re: help with R and GRASS6

> Well, I managed to get the residuals of the trend-surface analysis 
> in a
> Spatial data Frame.
> 
> Here's what I did:
> 
> 
> library(spgrass6) ; library(spatial);
> srtm <- getSites6sp("toposrtm");
> coords<-coordinates(srtm);
> class(srtm);
> G <- gmeta6();
> grd <- GridTopology(cellcentre.offset=c(G$west+(G$ewres/2),
> G$south+(G$nsres/2)), cellsize=c(G$ewres, G$nsres), 
> cells.dim=c(G$cols,G$rows));
> mask_SG <- SpatialGridDataFrame(grd, data=list(k=rep(1, 
> G$cols*G$rows)),proj4string=CRS(G$proj4));
> class(mask_SG);
> 
> trend <- surf.ls(1, x=coords[,1], y=coords[,2], z=srtm$cat);
> resid1<-residuals(trend);
> resid2<-as.data.frame(resid1);
> resid.trend<-SpatialPointsDataFrame(coords,resid2);
> resid.img <- SpatialGridDataFrame(grd, resid.trend);
> 
> 
> 
> Now I'll start playing with variograms and kriggind.
> 
> Thanks all!
> 
> Carlos
> 
> 
> On 2/21/06, Roger Bivand <Roger.Bivand at nhh.no> wrote:
> >
> > Hi Carlos,
> >
> > On Tue, 21 Feb 2006, Carlos "Guâno" Grohmann wrote:
> >
> > > Hello list
> > >
> > > I've away from R a while, and now I'm struggling with it...
> > > I read Bivand's artile in GRASS-News3, but I dindn't understant 
> exactly> how
> > > the data is stored in R.
> > >
> >
> > Please see a note in R News in November 2005 by Edzer Pebesma and 
> me.>
> > > If I want to make a trend-surface analysis with surf.ls(), I 
> need the
> > x,y
> > > and z coordinates of each point (or pixel), but I don't know 
> how to get
> > > these values
> >
> > The object returned by getSites6sp() is a SpatialPointsDataFrame. 
> You can
> > get the coordinates by saying:
> >
> > pointlayer <- getSites6sp("mypoints")
> > coords <- coordinates(pointlayer)
> >
> > and assuming z is called z:
> >
> > myTSA <- surf.ls(2, x=coords[,1], y=coords[,2], z=pointlayer$z)
> >
> > but you can also do TSA straight away in gstat:
> >
> > myTSA_with_gstat <- gstat(id="tr2", formula = z ~ 1, data = 
> pointlayer,>   degree=2)
> >
> > (the most recent gstat just takes the location coordinates from the
> > SpatialPointsDataFrame object.)
> >
> > There was a thread about this recently, I think copied to:
> >
> >
> > http://grass.gdf-
> hannover.de/twiki/pub/GRASS/WebHome/krigingusingRGRASS6.txt>
> > where a grid is created from the GRASS region settings to predict 
> to.>
> > Hope this helps,
> >
> > Roger
> >
> > >
> > > the whole idea is to make TSA, then variogram fitting in the 
> residuals,> then
> > > krigging (maybe with gstat or geoR, still haven't decided)
> > >
> > > thanks
> > >
> > > --
> > > +-----------------------------------------------------------+
> > >               Carlos Henrique Grohmann - Guano
> > >   Geologist M.Sc  - Doctorate Student at IGc-USP - Brazil
> > > Linux User #89721  - carlos dot grohmann at gmail dot com
> > > +-----------------------------------------------------------+
> > > _________________
> > > "Good morning, doctors. I have taken the liberty of removing 
> Windows 95
> > from
> > > my hard drive."
> > > --The winning entry in a "What were HAL's first words" contest 
> judged by
> > > 2001: A SPACE ODYSSEY creator Arthur C. Clarke
> > >
> >
> > --
> > 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
> >
> >
> 
> 
> --
> +-----------------------------------------------------------+
>              Carlos Henrique Grohmann - Guano
>  Geologist M.Sc  - Doctorate Student at IGc-USP - Brazil
> Linux User #89721  - carlos dot grohmann at gmail dot com
> +-----------------------------------------------------------+
> _________________
> "Good morning, doctors. I have taken the liberty of removing 
> Windows 95 from
> my hard drive."
> --The winning entry in a "What were HAL's first words" contest 
> judged by
> 2001: A SPACE ODYSSEY creator Arthur C. Clarke
>