

   EEvvaalluuaattee KKrriiggiinngg SSuurrffaaccee oovveerr aa GGrriidd

        prmat(obj, xl, xu, yl, yu, n)

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

        obj: object returned by `surf.gls'

         xl: limits of the rectangle for grid

         xu:

         yl:

         yu:

          n: use `n' x `n' grid within the rectangle

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

        Evaluate Kriging surface over a grid.

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

        list with components `x', `y' and `z' suitable for
        `contour' and `image'.

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

        `surf.gls', `trmat', `semat'

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

        data(topo)
        topo.kr <- surf.gls(2, expcov, topo, d=0.7)
        prsurf <- prmat(topo.kr, 0, 6.5, 0, 6.5, 50)
        contour(prsurf$x, prsurf$y, prsurf$z, levels=seq(700, 925, 25))

