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GEOSTATS: GEOSTAT: Exponential models in S-Plus and GEOEAS

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  • Alison_Riding@adas.co.uk
    This mail message, and any attachments, has been checked for Viruses by ADAS before dispatch to the Internet. Form: Memo Text: (38 lines follow) Since sending
    Message 1 of 1 , Mar 18, 1997
      This mail message, and any attachments, has been checked for Viruses
      by ADAS before dispatch to the Internet.


      Form: Memo
      Text: (38 lines follow)


      Since sending my first email about the problem I have been having with
      fitting exponential models in both geoas and s-plus, I have noticed that by
      changing the exp.vgram function in S-Plus

      from

      nugget + sill * (1 - exp( - distance/range))

      (which is often quoted as the exponential model, e.g. Haining p 97)

      to the following (which resembles that of Isaaks and Srivastava, page 374),

      nugget + sill * (1 - exp( - (3 * distance)/range))

      I then got the same fit as that in GEOAS.


      I am confused by this - and it seems a bit dangerous if different software
      uses different models, because we quote the semivariogram parameters and not
      the model format.

      Hope someone can help on this one -

      Alison
      ________________________________
      Dr Alison Riding
      ADAS
      Woodthorne
      Wolverhampton
      WV6 8TQ
      U.K.

      Tel: +44 (0) 1902 693129
      Fax: +44 (0) 1902 693166
      E-Mail: Alison_Riding@...
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