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AI-GEOSTATS: VARIOWIN

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  • ivan ortiz valencia
    HI list I got a problem using PREVAR 2d ( modulo of Variowin ).I used 1550 data points ( irregular ) and a message NOT ENOUGH MEMORY. But when I used another
    Message 1 of 2 , Nov 10, 2003
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      HI list

      I got a problem using PREVAR 2d ( modulo of Variowin ).I used 1550 data
      points ( irregular ) and a message NOT ENOUGH MEMORY. But when I used
      another sample, 251 points, It works well and the others modulos too.
      I do not know why, I used a computer with 512 mb RAM windows 2000.

      Any help is welcome.

      ivan


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    • ivan ortiz valencia
      I am sending the answers I got. Many Thanks to Maria, Oliver, Peter and Ed. IVAN ivan, or you have too many data points (i don t think so) or you are using an
      Message 2 of 2 , Nov 11, 2003
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        I am sending the answers I got. Many Thanks to Maria, Oliver, Peter and
        Ed.

        IVAN

        ivan,
        or you have too many data points (i don't think so) or you are using an
        invalid format in the input data. it must
        be GEO-EAS format.
        if you have too many data points i did the following:
        used GAMV, program of GSLIB, and then transformed de output format to fit
        that of VARIOWIN (see chapter 6 of Yvan
        Pannatier's VARIOWIN Manual) saving the file with VAR extension and then
        modelling with MODEL of VARIOWIN.
        best regards,
        maria.
        maria.morales@...
        -----------------------------------
        hi ivan, i once had the same problem......this is based in the fact that
        with 1500 points you've reached the maximal
        value of pairs that can be calculated by prevar 2d. try to minimise the
        maximum distances under setting or minimise
        your data set.........both worked fine for my data sets, which had an
        extent of almost 300 km (i minised the max
        distance to 15 km which was justifed from a technical point of view) and
        3000 ssampled locations.
        hope this helps,
        later,
        oliver
        oliver.sonnentag@...
        -----------------------------------
        Oi Ivan,

        this has happened to me as well (I had 6810 points). Remember that there
        are n*(n-1)/2 pairs = 1,200,475 in your case. I succeeded to process a
        maximum of 1500 data points which produces a pcf file ca. 20 MB large.
        I tried 2 alternatives:

        1) Use the option "max. lag" of PREVAR which restricts the max. distance
        of data points such that the resulting number of pairs is < 1500 (or
        whatever your computer can handle; mine had 64 MB Ram, Win 98). But be
        careful: This makes sense only if you have an idea of the length scale of
        the structure you are investigating, because if you restrict the max.
        distance you can miss a structure.

        2) Select a random sub-sample out of your original data sample, comprising
        < 1500 points, and use this random sub-sample for analysis. Repeat this
        several times in order to see if the variogram is +- the same. I used a
        simple self-made program for producing a random sub-sample. This method
        has worked well in my case, using random sub-samples each comprising 20%
        of the total data set.


        Another idea: If you have Surfer-7, try the variogram utility of the grid
        menu. Maybe it can handle such large amounts of data. It is also somewhat
        easier to use than Variowin.
        ---------------------------------------------
        good luck, pb

        Ivan

        May I suggest that you try SAGE2001 for all of your
        variogram calculations and modeling tasks.
        You will not have such problems with SAGE2001 and will
        find the modeling capabilities of SAGE2001 quite
        amazing. thanx, ed
        PS, go to www.isaaks.com to download the program.



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