## GEOSTATS: SAS PROC MIXED

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• Hi- Here is the answer to my question from earlier last week. Thanks for the responses everyone. Original question: Hi- Is anyone familiar with SAS PROC
Message 1 of 2 , Mar 31, 1999
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Hi-

Here is the answer to my question from earlier last week. Thanks for the
responses everyone.

Original question:

Hi-

Is anyone familiar with SAS PROC MIXED??

I am using it to fit semivariograms to spatially correlated data and
designed experiment data with spatially correlated errors.

Here is my technical question.

In SAS v 6.12 (current version), when the sill, range and nugget are
estimated as a spatial covariance structure (by using the command LOCAL in
the REPEATED statement) which covariance parameter estimates corresponds to
which parameter (range, sill or nugget) on the SAS output,

Here are 2 examples for spherical and gaussian covariance structures, For
the first one it makes sense that the estimates are nugget, range, sill (top
to bottom). But if this is true, in the second example the nugget would be
larger than the sill but this can't happen!!

Example 1
Covariance Parameter Estimates (REML)

Cov Parm Subject Estimate

Variance INTERCEPT 0.43177363
SP(SPH) INTERCEPT 54.78167843
Residual 1.04333638

Example 2
Covariance Parameter Estimates (REML)

Cov Par Subject Estimate
Variance INTERCEPT 2.07463337
SP(GAU) INTERCEPT 252.65941634
Residual 1.25734694

And a follow up question, Does SAS estimate the sill as an absolute value on
the y axis or as an increment above the nugget and the value of the max
semivariance???

The order is "sill, range, nugget", and "sill" here is
defined as the increment above the nugget. That is

sill + nugget = max semivariance

Deborah Keys

Quantitative Agronomist
Zeneca Ag Products
*(510) 231-1514
*deborah.d.a.keys@...

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