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AI-GEOSTATS: vertical semivariogram with gstat

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  • lisa pizzol
    Dear list members, I’m using GSTAT to build a 3D semivariogram, I find three directional semivariograms: Direction nug
    Message 1 of 2 , Jan 30, 2004
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      Dear list members,



      I’m using GSTAT to build a 3D semivariogram,

      I find three directional semivariograms:



      Direction nug psill range



      30 (in the plane) 0.25 0.19 805

      120 (in the plane) 0.25 0.19 687

      vertical 0.25 0.19 3.26



      I introduce in GSTAT this command:

      Sill range p q r s t

      vgm(0.19,”Gau”, 805, 0.25, anis=c(30, 0, 0, 0.85, 0.004))



      Where 0.85 = (687/805) and 0.004 = (3.26/805)



      When I plot this model with the sperimental semivariograms in the direction 30 and 120 (in the plane), this model works well because it follow the sperimental semivariogram but if I plot this model with the vertical semivariogram, it is a line around the value 0.25 while I expected that it reaches the sill (0.19+ 0.25) at 3.26 m. I tried to change the angles q and r, but if the model is good for the vertical direction then it doesn’t work with the other two directions (30 and 120).

      The command to find the vertical variogram was:

      > variogram(cadmiog, cuttoff=4, width=4/8,alpha=0, beta=90, tol.hor=90, tol.ver=15, cloud=FALSE).

      I apologise for this question but I’m at the beginning with GSTAT and I’m doing something wrong but I cannot understand where.



      Thank you very much for your attention,



      Best regards


      Lisa



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    • Edzer J. Pebesma
      ... I don t have your data, but think I can more or less reproduce your results. Directional variograms only plot (at least, the should plot) right, currently,
      Message 2 of 2 , Feb 4, 2004
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        lisa pizzol wrote:

        > Dear list members,
        >
        >
        >
        > I'm using GSTAT to build a 3D semivariogram,
        >
        > I find three directional semivariograms:
        >
        ...

        > The command to find the vertical variogram was:
        >
        > > variogram(cadmiog, cuttoff=4, width=4/8,alpha=0, beta=90,
        > tol.hor=90, tol.ver=15, cloud=FALSE).
        >
        > I apologise for this question but I'm at the beginning with GSTAT and
        > I'm doing something wrong but I cannot understand where.
        >
        >
        >
        I don't have your data, but think I can more or less reproduce your results.
        Directional variograms only plot (at least, the should plot) right,
        currently, when
        you pass a set of directions to the variogram command, and not when you pass
        a single direction. I will look into the issue, it is clearly a bug.
        --
        Edzer


        [Non-text portions of this message have been removed]
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