

   SSppaattiiaall CCoovvaarriiaannccee FFuunnccttiioonnss

        expcov(r, d, alpha=0, se=1)
        gaucov(r, d, alpha=0, se=1)
        sphercov(r, d, alpha=0, se=1, D=2)

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

          r: vector of distances at which to evaluate the
             covariance

          d: range parameter

      alpha: proportion of nugget effect

         se: standard deviation at distance zero

          D: dimension of spheres.

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

        Spatial covariance functions for use with `surf.gls'.

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

        vector of covariance values.

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

        `surf.gls', `correlogram'

