Provided by: libncarg-dev_6.3.0-6build1_amd64 NAME

c_ftkurvpd - interpolation and derivative calculation for closed parametric curves

FUNCTIONPROTOTYPE

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

SYNOPSIS

int c_ftkurvpd (n, xi, yi, m, t, xo, yo, xd, yd, xdd, ydd);

DESCRIPTION

n           The number of input data points. (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).

m           The number of desired interpolated points.

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,n-1.

yo          An array containing the Y values for the interpolated points.

xd          Contains the first derivatives of the X component with respect to t.

yd          Contains the first derivatives of the Y component with respect to t.

xdd         Contains the second derivatives of the X component with respect to t.

ydd         Contains the second derivatives of the Y component with respect to t.

RETURNVALUE

c_ftkurvpd 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 behaves like ftkurvp except that in  addition  it  returns  the  first  and
second derivatives of the component functions in the parameterization.

Given  a  sequence  of  distinct  input  points  ( (x,y), ... , (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,y)  and  the  value  1.  is mapped onto (x,y) as well
(completing the closed curve).

c_ftkurvpd 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_ftkurvpd 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_ftkurvpd, load the NCAR Graphics library ngmath.

SEEALSO

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