[Gstat-info] Initial exponential modal prior to fitting

[Mach Nife]

Hi Edzer,

As you suggested I used 10% of 1000m = 100m for the
range and for the sill: (Standard Deviation)^2=
0.245

Here's the formula:
0 nug()+ 0.245 exp(100)

After fitting using fit=1 the result is this:
Warning: singular model in variogram
fitvariogram(planting): 'planting.sem': 0.615988
Nug(0) + 1.79057 Exp(7949.84);

In ArcGIS Geostatistical Analyst, using the same
dataset and by letting the software calculate the
optimal settings, we get this autmatically optimized
formula (OK): 0.14372 Nugget + 0.16158
Exponential(952.21).

How come? Is there other resources (open source /
freeware) available that can be used as tools to
calculate optimal models?

Sincerely,
machnife

> --- "Edzer J. Pebesma" <e.pebesma at geo.uu.nl> wrote:
> 
> > Mach Nife wrote:
> > 
> > >I'm wondering, if I want to use the Exponential
> > >model, in a totally non-interactive way, what
> would
> > be
> > >a good initial formula to use prior to fitting? I
> > >noticed that with different initial formulas, the
> > >result of the fitting is different...
> > >
> > >Please escuse me for my lack of knowledge on this
> > >subject.
> > >
> > >machnife
> > >
> >
> >__________________________________________________
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>
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> > >  
> > >
> > I would choose a range parameter of 10% of the
> > spatial extent of the data area or volume, a zero
> > nugget and a sill equal to the sample variance.
> > --
> > Edzer
> > 
> > 
> 
> 
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