d. 16/04/01 17:44 skrev [EMAIL PROTECTED] på
[EMAIL PROTECTED]:
>
>
> Dear Colleagues
>
> I have learned that a valid variogram should be an even function, i.e.
> gamma(h)=gamma(-h). However, this condition is not satisfied by
> exponential variogram function. Am I missing something in this arguement?
Varograms and cross-variograms should be symmetric, but not
necessarily so for cross-covariances due to the lag effect
(different shape with lag direction). The confusion in most
texts is the -ve sign, when one actually deals with the
modulus (an absolute quantity) of h in the variogram calculations.
Cressie's notation should be clearer (in Spatial Data Analysis).
Syed
Copenhagen
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