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.