c_nnpntd - interpolate at a single point

       To use c_nnpntd, load the NCAR Graphics library ngmath.

       Copyright (C) 2000
       University Corporation for Atmospheric Research

       The use of this Software is governed by a License Agreement.

UNIX                                             March 1997-1998                                c_nnpntd(3NCARG)

       x           The X coordinate of the point where interpolation is desired.

       y           The Y coordinate of the point where interpolation is desired.

       z           *z is the interpolated functional value at the point (X,Y).

       void c_nnpntd(double, double, double *);

       c_nnpntd - interpolate at a single point

       natgrid, natgrid_params, c_natgrids, c_nnpntinitd, c_nnpntendd.

       Complete documentation for Natgrid is available at URL
       http://ngwww.ucar.edu/ngdoc/ng/ngmath/natgrid/nnhome.html

       void c_nnpntd (x, y, z);

       This  functino is called when you want to interpolate at an individal point.  c_nnpntinitd must be called
       prior to calling c_nnpntd.  c_nnpntendd must be called to terminate single point mode.