Hi,
I have a question about interpretation and
robustness of a variogram. My variogram rises then
plateaus and then rises again. I interpret this as
meaning that there are two scales at which there is
spatial dependence of the values. However, the number
of pairwise comparisons is quite different for each of
these stages and I am afraid I may just be seeing an
artifact of the sampling. I used variowin and when I
fit a model for just the first rise and plateau, the
sill was at about 1500 meters. The first point has 70
pairs and then from right before the plateau (1000 m)
to the beginning of the second rise, there are 324-396
pairs and finally the points in the second rise have
between 512-534 pairs. I have a total of 66 sample
points, but they are not evenly spaced with two areas
more heavily sampled than intervening areas.
Additional sampling is not feasible. Do I have a
problem? Is there a way to test the robustness of this
variogram (I don't know how to fit a model to a
variogram with two rises, so I couldn�t' do cross
validation)?
(Additional information - other data and analyzing the
same data with nested ANOVA, looking at smaller scales
within the data set, support the first rise. Taking
the residuals of a correlated variable - elevation -
removes the second rise but maintains the first rise -
my interpretation is that there are different
processes at the two scales).
I would appreciate any suggestions,
Thanks a lot,
Juliann Aukema
[EMAIL PROTECTED]
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