

   CCoommppuuttee SSppaattiiaall VVaarriiooggrraamm

        variogram(krig, nint, plotit=T, ...)

   AArrgguummeennttss::

       krig: trend-surface or kriging object with columns `x',
             `y', and `z'

       nint: number of bins used

     plotit: logical for plotting

        ...: parameters for the plot

   DDeessccrriippttiioonn::

        Divides range of data into `nint' bins, and computes
        the average squared difference for pairs with separa-
        tion in each bin.  Returns results for bins with 6 or
        more pairs.

   VVaalluuee::

        `x' and `y' coordinates of the variogram and `cnt', the
        number of pairs averaged per bin.

   SSiiddee EEffffeeccttss::

        Plots the variogram if `plotit = T'

   SSeeee AAllssoo::

        `correlogram'

   EExxaammpplleess::

          data(topo)
          topo.kr <- surf.ls(2, topo)
          variogram(topo.kr, 25)

