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AI-GEOSTATS: Crossvalidation

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  • Victoria Íñigo Mendoza
    Dear list members: I m doing my PhD about forestry soils and I use Idrisi 3.2 for my geostatistical analysis with Gstat interface. I do Ordinary Kriging and
    Message 1 of 2 , Aug 7, 2002
      Dear list members:
      I'm doing my PhD about forestry soils and I use Idrisi 3.2 for my
      geostatistical analysis with Gstat interface. I do Ordinary Kriging and
      after fitting the model when I do the crossvalidation I have to
      interpret this factors. Which of those have I pay attention in, to
      decide the best model?:

      corr(Obs, Pred): 0.1709 [using ordinary kriging]

      observed predicted pred.-obs. pred.std. zscore
      ======================================================================
      minimum 26.6 225.9 -3043 352 -8.528
      1st q. 224.6 379.8 -119.9 367.9
      -0.3343
      median 360.4 499.3 114 373.8 0.3052

      3rd q. 653.1 658.8 314.4 383.9
      0.8117
      maximum 3685 1658 1173 418.5 3.166

      n 118 118 118 118
      118
      mean 552.3 558.9 6.545 376.1 0.01326
      std.dev. 616.1 236.5 621 13.77 1.679


      Thanks and best regards
      Victoria Iñigo Mendoza
      University of La Rioja
      Spain


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    • Soeren Nymand Lophaven
      Dear Victoria Firstly, from the output you have displayed it seems to me that you should take the natural logarithm of your observations before doing the
      Message 2 of 2 , Aug 7, 2002
        Dear Victoria

        Firstly, from the output you have displayed it seems to me that you should
        take the natural logarithm of your observations before doing the spatial
        analysis.

        Secondly, if you want a measure of how well your model is predicting you
        could use sum((pred.-obs.)^2). That would in your case be the sum of 118
        squared differences. If you then try to predict your response using
        different types of models, you should chose the model with the lowest
        sum((pred.-obs.)^2).

        Best regards / Venlig hilsen

        Søren Lophaven
        ******************************************************************************
        Master of Science in Engineering | Ph.D. student
        Informatics and Mathematical Modelling | Building 321, Room 011
        Technical University of Denmark | 2800 kgs. Lyngby, Denmark
        E-mail: snl@... | http://www.imm.dtu.dk/~snl
        Telephone: +45 45253419 |
        ******************************************************************************

        On Wed, 7 Aug 2002, Victoria Íñigo Mendoza wrote:

        > Dear list members:
        > I'm doing my PhD about forestry soils and I use Idrisi 3.2 for my
        > geostatistical analysis with Gstat interface. I do Ordinary Kriging and
        > after fitting the model when I do the crossvalidation I have to
        > interpret this factors. Which of those have I pay attention in, to
        > decide the best model?:
        >
        > corr(Obs, Pred): 0.1709 [using ordinary kriging]
        >
        > observed predicted pred.-obs. pred.std. zscore
        > ======================================================================
        > minimum 26.6 225.9 -3043 352 -8.528
        > 1st q. 224.6 379.8 -119.9 367.9
        > -0.3343
        > median 360.4 499.3 114 373.8 0.3052
        >
        > 3rd q. 653.1 658.8 314.4 383.9
        > 0.8117
        > maximum 3685 1658 1173 418.5 3.166
        >
        > n 118 118 118 118
        > 118
        > mean 552.3 558.9 6.545 376.1 0.01326
        > std.dev. 616.1 236.5 621 13.77 1.679
        >
        >
        > Thanks and best regards
        > Victoria Iñigo Mendoza
        > University of La Rioja
        > Spain
        >
        >
        > --
        > * To post a message to the list, send it to ai-geostats@...
        > * As a general service to the users, please remember to post a summary of any useful responses to your questions.
        > * To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
        > * Support to the list is provided at http://www.ai-geostats.org
        >


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