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Re: New Fast Kriging Semivariogram Spherical Model Incorrect? [message #86176 is a reply to message #86172]

Wed, 16 October 2013 07:54

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

David Fanning writes:

> I have been writing a new cgKrig2D function for my own use that
provides
> orders of magnitude faster kriging for general use than the (extremely!)
> slow Krig2D function that is supplied with all currently released
> versions of IDL. In doing so, I have come to believe that the Spherical
> modeling function in both the old version of Krig2D and in the new
> version Chris released here last week is incorrect.

Now I think the Exponential modeling function is incorrect, too, based
on this reference (and the one I provided previously):

http://www.nbb.cornell.edu/neurobio/land/OldStudentProjects/ cs490-
94to95/clang/kriging.html

It is listed as:

r = t[2] * exp((-3./t[0]) * d)
r[WHERE(d eq 0, /NULL)] = t[1] + t[2]
return, r

According to my references, this should be:

r = t[2] * exp((-3./t[0]) * d)
r[WHERE(d eq 0 /NULL)] = 0
return, r

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")

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[Message index]

		New Fast Kriging Semivariogram Spherical Model Incorrect? By: David Fanning on Wed, 16 October 2013 07:10
		Re: New Fast Kriging Semivariogram Spherical Model Incorrect? By: David Fanning on Wed, 16 October 2013 07:54
		Re: New Fast Kriging Semivariogram Spherical Model Incorrect? By: chris_torrence@NOSPAM on Wed, 16 October 2013 21:00
		Re: New Fast Kriging Semivariogram Spherical Model Incorrect? By: David Fanning on Wed, 16 October 2013 21:20
		Re: New Fast Kriging Semivariogram Spherical Model Incorrect? By: chris_torrence@NOSPAM on Wed, 16 October 2013 21:24

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