NAME

       c_ftkurvp - interpolation for closed parametric curves

FUNCTION PROTOTYPE

       int c_ftkurvp (int, float [], float [], int, float [], float [], float []);

SYNOPSIS

       int c_ftkurvp (n, xi, yi, m, t, xo, yo);

DESCRIPTION

       n           The number of input data values. (n > 1)

       xi          An array containing the abscissae for the input function.

       yi          An array containing the functional values (y[k] is the functional value at x[k] for k=0,n-1).

       m           The number of desired interpolated values.

       t           Contains  an  array  of  values  for  the  parameter mapping onto the interpolated curve. Any
                   interval [tt,tt+1.] maps onto the entire curve.

       xo          An array containing the X values for the interpolated points.  t[k] maps to (xo[k],yo[k]) for
                   k=0,m-1.

       yo          An array containing the Y values for the interpolated points.  t[k] maps to (xo[k],yo[k]) for
                   k=0,m-1.

RETURN VALUE

       c_ftkurvp returns an error value as per:

       = 0 -- no error.
       = 1 -- if n is less than 2.
       = 2 -- if adjacent coordinate pairs coincide.

USAGE

       This procedure calculates an interpolatory spline under tension through a sequence of points in the plane
       forming a closed curve.

       Given a sequence of distinct input points ( (x[0],y[0]), ... , (x[n-1],y[n-1]), the interpolated curve is
       parameterized by mapping points in the interval [0.,1.] onto the interpolated curve. The resulting  curve
       has  a  parametric representation both of whose components are splines under tension and functions of the
       polygonal arc length. The value 0. is mapped onto (x[0],y[0]) and the value 1. is mapped onto (x[0],y[0])
       as well (completing the closed curve).

       c_ftkurvp is called after all of the desired values for  control  parameters  have  been  set  using  the
       procedures c_ftseti, c_ftsetr, c_ftsetc. The only control parameter that applies to c_ftkurvp is: sig.

       The  value for the parameter sig specifies the tension factor. Values near zero result in a cubic spline;
       large values (e.g. 50) result in nearly a polygonal line. A typical value is 1. (the default).

ACCESS

       To use c_ftkurvp, load the NCAR Graphics library ngmath.

SEE ALSO

       fitgrid_params, c_ftseti, c_ftsetr, c_ftsetc.

       Complete documentation for Fitgrid is available at URL
       http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html

COPYRIGHT

       Copyright (C) 2000
       University Corporation for Atmospheric Research

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

UNIX                                               March 1998                                  c_ftkurvp(3NCARG)