Provided by: libncarg-dev_6.1.2-7_amd64 
NAME
c_ftkurvd - calculate interpolated values and derivatives for parametric curves
FUNCTION PROTOTYPE
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.
RETURN VALUE
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[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[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[0],y[0]). 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.
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.