[STATSGRASS] different kriging results with the same parameters

[Carlos "Guâno" Grohmann]

Tryed. didn't work..

 OK_pred_md250 <- krige(band1 ~ 1, srtm2, mask_SG, model=vrg.eye, maxdist=250);

Error in model.frame(formula, rownames, variables, varnames, extras,
extranames,  :
        invalid variable type for 'band1'

Why do you think that the nugget variance would change anything?

tks



On 11/3/06, Edzer J. Pebesma <e.pebesma at geo.uu.nl> wrote:
> My only thought is try increasing the nugget variance; the Gaussian
> variogram model always triggers some kind of alarm. Still, output
> shouldn't vary.
>
> Have you tried replacing srtm$band1~1 with band1~1 (in which case it is
> taken from the second argument, srtm2)? Something like
>
> krige(band1 ~ 1, srtm2, mask_SG, model=vrg.eye, maxdist=250);
> --
> Edzer
>
> Carlos "Guâno" Grohmann wrote:
> > I was kriging some SRTM DEMs, and I noticed that I get different
> > results with the same parameters!!
> > check out:
> >
> > summary(srtm) - original data
> > Data attributes:
> >     band1
> > Min.   : 634.0
> > 1st Qu.: 759.0
> > Median : 814.0
> > Mean   : 856.5
> > 3rd Qu.: 923.0
> > Max.   :1312.0
> >
> > vrg.eye<-(vgm(psill=950, model="Gau", range=245, nugget=6.2));
> >
> > OK_pred_md250 <- krige(srtm$band1 ~ 1, loc=srtm2, newdata=mask_SG,
> > model=vrg.eye, maxdist=250);
> >
> >
> > summary(OK_pred_md250);
> > Data attributes:
> >   var1.pred         var1.var
> > Min.   : 632.8   Min.   :  8.054
> > 1st Qu.: 759.2   1st Qu.:  8.576
> > Median : 814.3   Median :  8.712
> > Mean   : 856.4   Mean   :  9.052
> > 3rd Qu.: 923.6   3rd Qu.:  8.865
> > Max.   :1307.6   Max.   :395.609
> >
> > Data attributes:
> >   var1.pred         var1.var
> > Min.   : 632.4   Min.   :  8.040
> > 1st Qu.: 759.2   1st Qu.:  8.577
> > Median : 814.3   Median :  8.711
> > Mean   : 856.4   Mean   :  9.048
> > 3rd Qu.: 923.6   3rd Qu.:  8.863
> > Max.   :1306.2   Max.   :341.567
> >
> > Data attributes:
> >   var1.pred         var1.var
> > Min.   : 632.9   Min.   :  8.039
> > 1st Qu.: 759.2   1st Qu.:  8.576
> > Median : 814.3   Median :  8.712
> > Mean   : 856.4   Mean   :  9.052
> > 3rd Qu.: 923.6   3rd Qu.:  8.865
> > Max.   :1306.9   Max.   :345.084
> >>
> >
> >
> > So, the minimum and maximum have changed each time. Why?
> >
> > thanks
> >
>
>


-- 
+-----------------------------------------------------------+
              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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