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GEOSTATS: nugget effect

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  • Donald Myers
    The nugget effect is composed of at least two components, one is very short range variability (shorter than the smallest inter-sample distance) and secondly
    Message 1 of 1 , Jun 1, 1998
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      The nugget effect is composed of at least two components, one is very short
      range variability (shorter than the smallest inter-sample distance) and
      secondly the noise-error componet of the data. Usually one does not have
      data to separately estimate the latter but if data is available one can
      use it in at least two ways, one is estimate/model the nugget effect (which
      could be greater than the variance of the error component) and secondly one
      can modify the kriging equations to allow smoothing as well as
      interpolation. In the latter case the kriging estimator is no longer exact.


      Given that you have a skewed distribution, you might want to consider a
      data transformation such as logarithmic.

      Also as an additional way of considering the size of the nugget term, you
      might want to look at cross-validation results. This can also be helpful in
      detecting unusual data values and locations. It might be useful to
      temporarily delete these and re-model the variogram and again consider
      cross validation results (both with the unusual values included and with
      them suppressed).

      Donald E. Myers
      Department of Mathematics
      University of Arizona
      Tucson, AZ 85721
      (520) 621-6859
      myers@...

      http://www.u.arizona.edu/~donaldm

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