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AI-GEOSTATS: about gstat and the variogram cloud

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  • lisa pizzol
    Dear list members, I’m using GSTAT (in S-Plus) to build a 3D semi-variogram. I have about 1300 samples, I built a directional variogram and I created a
    Message 1 of 2 , Jan 26, 2004
      Dear list members,



      I’m using GSTAT (in S-Plus) to build a 3D semi-variogram. I have about 1300 samples, I built a directional variogram and I created a related file with the variogram cloud (about 110000 pairs). My problem is that I can not print this file (print.variogram.cloud), the program says that it makes a bad operation and it closes itself; is it because this file is too large? if I go to the Object Editor I can open this file file but I can not see the numbers of the samples that form the pairs (there are not the columns “left” and “right” (for variogram.cloud: data id (row number) of one of the data pair) like I expected). Instead of these columns there is the column called “np” (the number of point pairs for this estimate) that shouldn’t be in this file but only in the variogram file. The column “np” has strange numbers that I can not understand. Can I calculate the data id (row number) of the samples of a pair from the numbers in the “np” column? where did I go wrong?

      Thank you very much.

      Best regards,


      Lisa



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    • Edzer J. Pebesma
      Lisa, you are right: gstat uses np to encode the information about which point pairs contribute to a single variogram cloud point.The relation between np and
      Message 2 of 2 , Jan 26, 2004
        Lisa, you are right: gstat uses np to encode the information
        about which point pairs contribute to a single variogram
        cloud point.The relation between np and the left and
        right field are found in the function print.variogram.cloud:

        function (x, ...)
        {
        x$left = x$np%%2^16 + 1
        x$right = x$np%/%2^16 + 1
        x$np = NULL
        print(data.frame(x), ...)
        }

        Furthermore, I cannot reproduce your problem; in
        S-Plus 6.1r1 for Windows, I get:

        > n=1300
        > x=data.frame(x=runif(n),y=runif(n),z=runif(n),v=rnorm(n))
        > x.vc=variogram(v~1,~x+y+z,x,cloud=T)
        > x.vc[1:10,]
        dist gamma dir.hor dir.ver id left right
        1 0.4339541 0.0044311723 0 0 1 3 2
        2 0.3170554 1.6191470800 0 0 1 4 2
        3 0.2289803 1.7929856870 0 0 1 4 3
        4 0.4712303 3.6202814606 0 0 1 5 1
        5 0.4258145 0.1108600917 0 0 1 5 2
        6 0.5333062 0.8826612122 0 0 1 5 4
        7 0.3405685 3.7223526406 0 0 1 6 1
        8 0.4752595 0.8333212054 0 0 1 6 4
        9 0.4408808 0.0007094885 0 0 1 6 5
        10 0.2938981 1.0232285872 0 0 1 7 3
        >

        Maybe you forgot to load the gstat library before
        your call to print.variogram.cloud?
        --
        Edzer

        lisa pizzol wrote:

        > Dear list members,
        >
        > I’m using GSTAT (in S-Plus) to build a 3D semi-variogram. I have about
        > 1300 samples, I built a directional variogram and I created a related
        > file with the variogram cloud (about 110000 pairs). My problem is that
        > I can not print this file (print.variogram.cloud), the program says
        > that it makes a bad operation and it closes itself; is it because this
        > file is too large? if I go to the Object Editor I can open this file
        > file but I can not see the numbers of the samples that form the pairs
        > (there are not the columns “left” and “right” (for variogram.cloud:
        > data id (row number) of one of the data pair) like I expected).
        > Instead of these columns there is the column called “np” (the number
        > of point pairs for this estimate) that shouldn’t be in this file but
        > only in the variogram file. The column “np” has strange numbers that I
        > can not understand. Can I calculate the data id (row number) of the
        > samples of a pair from the numbers in the “np” column? where did I go
        > wrong?
        >
        > Thank you very much.
        >
        > Best regards,
        >
        > Lisa
        >


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