AI-GEOSTATS: modelling and goodness of fit

2007-09-13 Thread Andrea Sciarretta 
Hi,

I'm working on variogram modelling and in the majority of cases only R2 is
available to evaluate the best-fit values, but in cases of non-linear
functions, it is very criticized.

 Are there other standard methods to evaluate the goodness of a fit of a
non-linear function (for example asymptotic confidence intervals) and how to
calculate them, considering that the majority of geostatistical software do
not perform any alternative coefficient?

Thank you

Andrea

Re: AI-GEOSTATS: modelling and goodness of fit

2007-09-13 Thread Edzer J. Pebesma 

Andrea, have you considered maximum likelihood fitting?
--
Edzer

Andrea Sciarretta wrote:


Hi,

I’m working on variogram modelling and in the majority of cases only 
R2 is available to evaluate the best-fit values, but in cases of 
non-linear functions, it is very criticized.


Are there other standard methods to evaluate the goodness of a fit of 
a non-linear function (for example asymptotic confidence intervals) 
and how to calculate them, considering that the majority of 
geostatistical software do not perform any alternative coefficient?


Thank you

Andrea


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Re: AI-GEOSTATS: modelling and goodness of fit

2007-09-13 Thread Isobel Clark 
Andrea
   
  We use Cressie's goodness of fit statistic which allows for number of pairs 
and other factors in semi-veriogram fitting. You can find a paper of his in 
Methematical Geology around 1992, or in his book. It is also illustrated in our 
free tutorial material at www.kriging.com
   
  Isobel

Andrea Sciarretta [EMAIL PROTECTED] wrote:
Hi,
  I’m working on variogram modelling and in the majority of cases only R2 is 
available to evaluate the best-fit values, but in cases of non-linear 
functions, it is very criticized.
   Are there other standard methods to evaluate the goodness of a fit of a 
non-linear function (for example asymptotic confidence intervals) and how to 
calculate them, considering that the majority of geostatistical software do not 
perform any alternative coefficient?
  Thank you
  Andrea