[STATSGRASS] Trend surface analysis issue - sending results back to GRASS

[Carlos "Guâno" Grohmann]

Roger, I'm still lost :)

let's see:


>library(spgrass6) ; library(spatial); library(gstat); library(lattice);
>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));

>pts_trend<- getSites6sp("points_trend2");

> summary(pts_trend)
Object of class SpatialPointsDataFrame
Coordinates:
                min       max
coords.x1  293529.5  297411.7
coords.x2 8873992.2 8878313.7
Is projected: TRUE
proj4string : [+proj=utm +south +zone=24 +a=6378160 +rf=298.25
+no_defs +towgs84=-60.0,-2.0,-41.0]
Number of points: 31
Data attributes:
      cat             x                y                alt
 Min.   : 1.0   Min.   :293530   Min.   :8873992   Min.   :514.4
 1st Qu.: 8.5   1st Qu.:294619   1st Qu.:8874820   1st Qu.:522.8
 Median :16.0   Median :295493   Median :8875555   Median :533.0
 Mean   :16.0   Mean   :295542   Mean   :8875925   Mean   :536.8
 3rd Qu.:23.5   3rd Qu.:296673   3rd Qu.:8877029   3rd Qu.:550.4
 Max.   :31.0   Max.   :297412   Max.   :8878314   Max.   :571.3

******************************************************************
now gstat:

>tbv_trend2_gstat <- gstat(id="tr2", formula = alt ~ 1, data =
pts_trend2, degree=2);

> names(tbv_trend2_gstat)
[1] "data"  "model" "call"


And I am here... I don't know how to display the results or how to get
it back in GRASS, how to do analysis of variance among trend surfaces
of different degrees... If I use surf.ls(), I can get the anova table
but I don't know how to get the image or anything else..


Carlos






On 9/27/06, Roger Bivand <Roger.Bivand at nhh.no> wrote:
> On Wed, 27 Sep 2006, Carlos "Guâno" Grohmann wrote:
>
> > Hello all
> >
> > Since the new sp and spGRASS6 packages, I haven't done any trand
> > surface analysis yet, so I'm a little lost here..
> >
> > in the old day, I would do this:
> >
> > g1r<-surf.ls(1,gradiente$east,gradiente$north,gradiente$num1);
> >  g1g<-trmat.G(G,g1r);
> >  rast.put(G,lname="gradiente.trend1",layer=g1g);
> >
> > now that trmat.G doesen't exists anymore, how do I do to send my trend
> > sufaces back to GRASS?
>
> Use the standard gstat() approach, with the degree= argument. The gstat
> package and surf.ls() in MASS use the same coordinate shrinking approach
> and give the same results.
>
> Roger
>
> >
> > thanks
> >
> > Carlos
> >
> >
>
> --
> 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
+-----------------------------------------------------------+
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