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

c_ftkurvd - calculate interpolated values and derivatives for parametric curves

FUNCTIONPROTOTYPE

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

SYNOPSIS

int c_ftkurvd (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.

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_ftkurvd 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 ftkurv except that in addition it returns the first and second
derivatives of the component functions in the parameterization.

Given  a  sequence  of 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[n-1],y[n-1]).

c_ftkurvd  is  called after all of the desired values for control parameters have been set
using the procedures c_ftseti,  c_ftsetr,  c_ftsetc.  Control  parameters  that  apply  to
c_ftkurvd are: sig, sl1, sln, sf1.

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).

The value for parameter sl1 is in radians and contains the slope at (x,y). The angle
is measured counter-clockwise from the X axis and the  positive  sense  of  the  curve  is
assumed  to  be  that  moving from point 0 to point n-1. A value for sl1 may be omitted as
indicated by the switch sf1.

The value for parameter sln is in radians and contains the slope at  (x[n-1],y[n-1]).  The
angle is measured counter-clockwise from the X axis and the positive sense of the curve is
assumed to be that moving from point 0 to point n-1. A value for sln  may  be  omitted  as
indicated by the switch sf1.

The  value  of  sf1  controls  whether to use the values for sl1 and sln, or compute those
values internally.  Specifically, sf1

= 0 if sl1 and sln are user-specified.
= 1 if sl1 is user-specified, but sln is
internally calculated.
= 2 if sln is user-specified, but sl1 is
internally calculated.
= 3 if sl1 and sln are internally calculated.

ACCESS

To use c_ftkurvd, 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