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AI-GEOSTATS: Declustering

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  • oliver.sonnentag@web.de
    hello list, to get the global mean of my data set (484 observation wells) and as a prerequisite for Normal Score Transformation with GSLIB, i declustered my
    Message 1 of 7 , Jul 5, 2003
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      hello list,
      to get the global mean of my data set (484 observation wells) and
      as a prerequisite for Normal Score Transformation with GSLIB, i
      declustered my data with polygonal declustering. When
      standardizing the weights to 1, so that the weights sum up to the
      number of data, I receive some negative weights. this results in
      negative values for the observations (nitrate concentration). how do
      i have to interpret this ? does this require a special treatment? skip
      them? as I mentioned before, i want to normal score transform the
      data set prior to simple kriging.
      many many thanx for some help in advance.
      Regards,
      Oliver




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    • Michael Pyrcz
      Good day Oliver, I have another comment on declustering in addition to the previous comment on negative weights. The weights do not actually change the data
      Message 2 of 7 , Jul 5, 2003
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        Good day Oliver,

        I have another comment on declustering in addition to the previous
        comment on negative weights. The weights do not actually change the
        data values. They change the weight of the data values within the
        distribution; therefore, weights change the distribution, but not the
        sample data. One way to think of declustering weights is that they
        would change the height on the bars of a histogram (more precisely, the
        contribution of each of the data to the bar height), but not the
        position of the bars.

        The GSLIB book (Deutsch and Journel) has a lot of practical guides to
        declustering. I have recently written a paper on the specifics of
        declustering, if you are interested.

        All the best,

        Michael

        _____________________________________________

        Michael Pyrcz
        Ph.D. Candidate
        Department of Civil & Environmental Engineering
        University of Alberta
        (780) 492-3153
        mpyrcz@...
        www.ualberta.ca/~mpyrcz


        -----Original Message-----
        From: ai-geostats-list@... [mailto:ai-geostats-list@...] On
        Behalf Of oliver.sonnentag@...
        Sent: July 5, 2003 2:13 AM
        To: ai-geostats@...
        Subject: AI-GEOSTATS: Declustering

        hello list,
        to get the global mean of my data set (484 observation wells) and
        as a prerequisite for Normal Score Transformation with GSLIB, i
        declustered my data with polygonal declustering. When
        standardizing the weights to 1, so that the weights sum up to the
        number of data, I receive some negative weights. this results in
        negative values for the observations (nitrate concentration). how do
        i have to interpret this ? does this require a special treatment? skip
        them? as I mentioned before, i want to normal score transform the
        data set prior to simple kriging.
        many many thanx for some help in advance.
        Regards,
        Oliver




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