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Re: GEOSTATS: Test for spatial randomness

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  • Rane Curl
    ... Randomly distributed over what? --Rane L. Curl -- *To post a message to the list, send it to ai-geostats@gis.psu.edu. *As a general service to list users,
    Message 1 of 4 , Feb 12, 1999
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      On Fri, 12 Feb 1999, Dan Hough wrote:

      > We have a graduate student who has been studying coastal dolphins in
      > Nicaragua for the last three years. She would like to be able to do a
      > statistical test that will tell her that her sightings are (or are not)
      > randomly distributed.
      > We are looking for a test that would work on her presence data.

      Randomly distributed over what?

      --Rane L. Curl


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    • Daniel Bebber
      I suppose what you want is to see if each observation in independent in space and time, or whether they are clustered. You can use variography on binary data
      Message 2 of 4 , Feb 15, 1999
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        I suppose what you want is to see if each observation in independent in
        space and time, or whether they are clustered. You can use variography on
        binary data (as described in Isaaks and Srivastava) to see if there is
        dependence, as long as you know the points in Euclidean space and time where
        the dolphins appeared. There are also tests of significance, but I'm not
        well-versed in them. As others have noted, if dolphins do behave randomly
        and independently then we will have to fundamentally alter our world view.
        ____________________________
        Daniel P. Bebber

        Department of Plant Sciences
        University of Oxford
        South Parks Road
        Oxford OX1 3RB
        Tel. 01865 275000
        Fax. 01865 275074



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      • Dan Wartenberg
        The traditional approach to test for spatial randomness is to test for spatial autocorrelation (similar to variography) using any of a number of specific
        Message 3 of 4 , Feb 15, 1999
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          The traditional approach to test for spatial randomness is to test for
          spatial autocorrelation (similar to variography) using any of a number of
          specific indices. The best reference I know of is still Cliff and Ord
          1981 although the methods are presented in Cressie's book, Uppton's book,
          Bailey's book, etc. Also many articles.

          Daniel Wartenberg
          Environmental and Occupational Health Sciences Institute
          170 Frelinghuysen Road, Piscataway, NJ 08855
          voice: 732-445-0197 fax: 732-445-0784 email: dew@...

          On Mon, 15 Feb 1999, Daniel Bebber wrote:

          > I suppose what you want is to see if each observation in independent in
          > space and time, or whether they are clustered. You can use variography on
          > binary data (as described in Isaaks and Srivastava) to see if there is
          > dependence, as long as you know the points in Euclidean space and time where
          > the dolphins appeared. There are also tests of significance, but I'm not
          > well-versed in them. As others have noted, if dolphins do behave randomly
          > and independently then we will have to fundamentally alter our world view.
          > ____________________________
          > Daniel P. Bebber
          >
          > Department of Plant Sciences
          > University of Oxford
          > South Parks Road
          > Oxford OX1 3RB
          > Tel. 01865 275000
          > Fax. 01865 275074
          >
          >
          >
          > --
          > *To post a message to the list, send it to ai-geostats@....
          > *As a general service to list users, please remember to post a summary
          > of any useful responses to your questions.
          > *To unsubscribe, send email to majordomo@... with no subject and
          > "unsubscribe ai-geostats" in the message body.
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          >


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