

   CCoommppuuttee SSppaattiiaall CCoorrrreellooggrraammss

        correlogram(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 covariance for pairs with separation in each bin,
        then divides by the variance.  Returns results for bins
        with 6 or more pairs.

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

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

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

        Plots the correlogram if `plotit = T'.

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

        `variogram', `expcov'

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

          data(topo)
          topo.kr <- surf.ls(2, topo)
          correlogram(topo.kr, 25)
          d <- seq(0, 7, 0.1)
          lines(d, expcov(d, 0.7))

