variogram fitting...

[Chris Skelly]

Hi Guys,

I have cross-posted this to a couple news groups, sorry for
wasting band width, but there might be a couple people out
there who can help.

I am working on implementing the generalised least-squares
fitting routine from Numerical Recipes in order to have a
more robust fitting of my variograms, which are in turn 
needed for kriging.  

I am stuck on how to code up the "user supplied" function
for spherical variograms.  This is where you need to derive
the function into its basis component functions.  I have
been trying to follow Cressie (1985), by my maths are 
obviously not up to taking his equation on page 576 to
the coding stage.  It also needs to be implemented iteratively.
Has anyone done this?  In any form?

Cheers,
Chris

Cressie, N.A.C. (1985) Fitting Variogram Models by Weighted
Least Squares, Math. Geol. 17, 5.
-- 
|\/\/\/|                             Chris Skelly
|      |                             School of Earth Sciences 
|      |   High expolsives and       Macquarie University  
|  (o)(o)   school do NOT mix.       North Ryde, 2109, NSW, OZ 
C       _)                           Tel: 612-805-8433 
 |  ,___|                            Fax: 612-805-8428 
 |    /  chris at mqclimat.cic.mq.edu.au