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AI-GEOSTATS: Interpretation of rho and its control in Splus

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  • Volker Bahn
    Dear List members, What would be a good interpretation for the coefficient Rho in a conditional autoregressive (CAR) model? I have looked through the
    Message 1 of 2 , Oct 16, 2003
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      Dear List members,

      What would be a good interpretation for the coefficient Rho in a conditional autoregressive (CAR) model?
      I have looked through the literature (Cressie and such) but haven't found a good verbal interpretation. Is it fair to say that the larger rho, the stronger the spatial effect.

      Also, does someone on this list know how to control rho in Splus? I would like to force it to 0 occasionally to get a "null" model for Rsquare and AIC calculations.

      Thank you

      Volker Bahn

      -~^/\^~^/\~/\^~^^/\/\~^~*

      Dept. of Wildlife Ecology - Rm. 210
      University of Maine
      5755 Nutting Hall
      Orono, Maine
      04469-5755, USA
      Tel: (207) 581 2799
      Fax: (207) 581 2858


      [Non-text portions of this message have been removed]
    • Roger Bivand
      ... Yes and no. Larger absolute values would indicate stronger spatial effects, larger positive values stronger positive spatial autocorrelation reducing the
      Message 2 of 2 , Oct 17, 2003
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        On Thu, 16 Oct 2003, Volker Bahn wrote:

        > Dear List members,
        >
        > What would be a good interpretation for the coefficient Rho in a
        > conditional autoregressive (CAR) model? I have looked through the
        > literature (Cressie and such) but haven't found a good verbal
        > interpretation. Is it fair to say that the larger rho, the stronger the
        > spatial effect.

        Yes and no. Larger absolute values would indicate stronger spatial
        effects, larger positive values stronger positive spatial autocorrelation
        reducing the effective number of observations. Robert Haining's new book
        on "Spatial Data Analysis" is a good source on these kinds of questions
        (2003, Cambridge UP).

        >
        > Also, does someone on this list know how to control rho in Splus? I
        > would like to force it to 0 occasionally to get a "null" model for
        > Rsquare and AIC calculations.
        >

        Perhaps just fit lm(), AIC should be OK, as should the likelihood ratio
        test. I don't have access to the software, so I'm generalising from how
        similar classes work in R.


        > Thank you
        >
        > Volker Bahn
        >
        > -~^/\^~^/\~/\^~^^/\/\~^~*
        >
        > Dept. of Wildlife Ecology - Rm. 210
        > University of Maine
        > 5755 Nutting Hall
        > Orono, Maine
        > 04469-5755, USA
        > Tel: (207) 581 2799
        > Fax: (207) 581 2858
        >

        --
        Roger Bivand
        Economic Geography Section, Department of Economics, Norwegian School of
        Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
        Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
        e-mail: Roger.Bivand@...


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