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[ai-geostats] discriminant analysis?

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  • MARTINEZ VARGAS Adrian
    hello mail list I have a categorical variable that describe rock type and I m interesting in quantify the relation and discriminant capacity of continuous
    Message 1 of 4 , Mar 16, 2005
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      hello mail list

      I have a categorical variable that describe rock type and I'm
      interesting in quantify the relation and discriminant capacity of
      continuous variables (grade elements) over each category.

      The problem is that I have no normality over the domain and the classes,
      the variance and covariances are not the same, and the categories are
      not independent, that limit for example the Discriminant analysis, some
      alternative (example logistic regression )?

      a) what to use as statistical method?
      b) is possible to use discriminant analysis?

      Regards
      Adrian Martínez
    • Chris Hlavka
      Re : Use of discriminant analysis: You might try quadratic disciminant analysis, wherein differences among variances and covariances are taken into account.
      Message 2 of 4 , Mar 16, 2005
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        Re : Use of discriminant analysis: You might try quadratic
        disciminant analysis, wherein differences among variances and
        covariances are taken into account. You don't describe how far the
        class distributions are from being normally distributed - but in some
        cases data transformations (e.g. applying the log transformation to
        skewed data) will make the data normally distributed or almost so.
        In any case, it's a good idea to get a measure of performance -
        splitting data with class identifications into training (for
        computing discriminants) and test (for computing accuracy of
        discriminat anaoysis) subsets if you have sufficient data, or
        jacknifing in the case of fewer data.

        >hello mail list
        >
        >I have a categorical variable that describe rock type and I'm
        >interesting in quantify the relation and discriminant capacity of
        >continuous variables (grade elements) over each category.
        >
        >The problem is that I have no normality over the domain and the classes,
        >the variance and covariances are not the same, and the categories are
        >not independent, that limit for example the Discriminant analysis, some
        >alternative (example logistic regression )?
        >
        >a) what to use as statistical method?
        >b) is possible to use discriminant analysis?
        >
        >Regards
        >Adrian Martínez
        >
        >
        >
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        --
        ***************************************
        Chris Hlavka
        NASA/Ames Research Center 242-4
        Moffett Field, CA 94035-1000
        (650)604-3328 FAX 604-4680
        Christine.A.Hlavka@...
        ***************************************
      • Mahdi Osman
        Hi, Martinez, It seems to me that you are analysing coded categorical variables (eg. soft = 1, coarse = 2, hard = 3 etc.). I also assume that your coding is
        Message 3 of 4 , Mar 16, 2005
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          Hi, Martinez,

          It seems to me that you are analysing coded categorical variables (eg. soft
          = 1, coarse = 2, hard = 3 etc.). I also assume that your coding is not
          reflecting any inherent characteristics of your rocks or your objects of
          examination.

          To be able to answer your question I would like to know the nature of your
          response variable (usually called regressand or predictand etc.). Especially
          I would like to know if it is a continuous variable or a categorical
          variable. If it is a categorical variable, how many levels do you have for
          it? Bionomial or multinomial? Ordered or nomial?

          If you have bionomial dependent variable you can use logistic regression or
          binary probit. Even though their distribution assumptions are different, the
          final conclusion will be the same. If you have ordered variable, you can use
          ologit (ordered logit) or oprobit (ordered probit). If you have multi-level
          nominal variable, you can use multinomial regression analysis.

          You can use discriminat analysis, but I would rather go for logist or probit
          methods as they are more advanced and any way will answer your quesions.

          If you need more help, pleas contact me.

          I hope this helps a little bit.

          Cheers
          Mahdi

          > hello mail list
          >
          > I have a categorical variable that describe rock type and I'm
          > interesting in quantify the relation and discriminant capacity of
          > continuous variables (grade elements) over each category.
          >
          > The problem is that I have no normality over the domain and the classes,
          > the variance and covariances are not the same, and the categories are
          > not independent, that limit for example the Discriminant analysis, some
          > alternative (example logistic regression )?
          >
          > a) what to use as statistical method?
          > b) is possible to use discriminant analysis?
          >
          > Regards
          > Adrian Martínez
          >
          >
          >
          >

          --
          -----------------------------------
          Mahdi Osman (PhD)
          E-mail: m_osm@...
          -----------------------------------

          DSL Komplett von GMX +++ Supergünstig und stressfrei einsteigen!
          AKTION "Kein Einrichtungspreis" nutzen: http://www.gmx.net/de/go/dsl
        • gpezzuchi@way.com.ar
          Hi all: Sorry to disturb with a different question, I was wondering if anyone could point out some good references on multilevel modeling within a spatial
          Message 4 of 4 , Mar 18, 2005
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            Hi all:

            Sorry to disturb with a different question, I was wondering if anyone could
            point out some good references on multilevel modeling within a spatial
            framework, besides the work of the folks creators of Mlwin.

            Thanks in advance,

            Gaston Pezzuchi

            Mensaje citado por MARTINEZ VARGAS Adrian <martinez@...>:

            > hello mail list
            >
            > I have a categorical variable that describe rock type and I'm
            > interesting in quantify the relation and discriminant capacity of
            > continuous variables (grade elements) over each category.
            >
            > The problem is that I have no normality over the domain and the classes,
            > the variance and covariances are not the same, and the categories are
            > not independent, that limit for example the Discriminant analysis, some
            > alternative (example logistic regression )?
            >
            > a) what to use as statistical method?
            > b) is possible to use discriminant analysis?
            >
            > Regards
            > Adrian Martínez
            >
            >
            >
            >




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