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[ai-geostats] Re: kriging proportions

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  • Isobel Clark
    Marc-Olivier The simplest solution - in the sense that most packages could handle it - is to carry out a nested indicator analysis. That is: (i) code one of
    Message 1 of 1 , Jun 10, 2004
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      Marc-Olivier

      The simplest solution - in the sense that most
      packages could handle it - is to carry out a 'nested'
      indicator analysis.

      That is:

      (i) code one of your particle classes as '1' and all
      other as '0', produce a map of proportion of this
      class.

      (ii) remove this particle class from your data. Code
      the next class as 1 and all others as 0. produce a map
      of "the proportion of this class, given that it is not
      in the first class". The 'actual' proportion is then
      P(ii)*(1-P(i)).

      (iii) If you have more than three classes, you can
      keep nesting although you tend to run out of data
      pretty fast. The last class has whatever proportion is
      left.

      Proportions such as this which have to add up to 1 or
      100% have been the subject of a lot of study,
      particularly by people such as Vera Pawlowsky-Glahn
      under the title 'compositional data'.

      Isobel
      http://geoecosse.bizland.com/BYOGeostats.htm





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