c_ftkurv - interpolation for parametric curves
int c_ftkurv (int, float [], float [], int, float [], float [], float []);
int c_ftkurv (n, xi, yi, m, t, xo, yo);
- 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.
- 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.
c_ftkurv returns an error value as per:
= 0 -- no error.
= 1 -- if n is less than 2.
= 2 -- if adjacent coordinate pairs coincide.
This function calculates an interpolatory spline under tension through a
sequence of points in the plane.
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_ftkurv 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_ftkurv 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.
To use c_ftkurv, load the NCAR Graphics library ngmath.
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 (C) 2000
University Corporation for Atmospheric Research
The use of this Software is governed by a License Agreement.