1c_ftkurv(3NCARG)                 NCAR GRAPHICS                c_ftkurv(3NCARG)
2
3
4

NAME

6       c_ftkurv - interpolation for parametric curves
7

FUNCTION PROTOTYPE

9       int  c_ftkurv  (int, float [], float [], int, float [], float [], float
10       []);
11

SYNOPSIS

13       int c_ftkurv (n, xi, yi, m, t, xo, yo);
14

DESCRIPTION

16       n           The number of input data values. (n > 1)
17
18       xi          An array containing the abscissae for the input function.
19
20       yi          An array containing the  functional  values  (y[k]  is  the
21                   functional value at x[k] for k=0,n-1).
22
23       m           The number of desired interpolated values.
24
25       t           Contains  an array of values for the parameter mapping onto
26                   the interpolated curve.
27
28       xo          An array containing  the  X  values  for  the  interpolated
29                   points.  t[k] maps to (xo[k],yo[k]) for k=0,m-1.
30
31       yo          An  array  containing  the  Y  values  for the interpolated
32                   points.  t[k] maps to (xo[k],yo[k]) for k=0,m-1.
33

RETURN VALUE

35       c_ftkurv returns an error value as per:
36
37       = 0 -- no error.
38       = 1 -- if n is less than 2.
39       = 2 -- if adjacent coordinate pairs coincide.
40

USAGE

42       This function calculates an interpolatory spline under tension  through
43       a sequence of points in the plane.
44
45       Given  a sequence of input points ( (x[0],y[0]), ... , (x[n-1],y[n-1]),
46       the interpolated curve is parameterized by mapping points in the inter‐
47       val  [0.,1.]  onto  the  interpolated  curve. The resulting curve has a
48       parametric representation both of whose components  are  splines  under
49       tension  and  functions  of  the  polygonal arc length. The value 0. is
50       mapped  onto  (x[0],y[0])   and   the   value   1.   is   mapped   onto
51       (x[n-1],y[n-1]).
52
53       c_ftkurv  is called after all of the desired values for control parame‐
54       ters have been set using the procedures c_ftseti,  c_ftsetr,  c_ftsetc.
55       Control parameters that apply to c_ftkurv are: sig, sl1, sln, sf1.
56
57       The  value  for the parameter sig specifies the tension factor.  Values
58       near zero result in a cubic spline; large values (e.g.  50)  result  in
59       nearly a polygonal line. A typical value is 1. (the default).
60
61       The  value  for  parameter  sl1 is in radians and contains the slope at
62       (x[0],y[0]). The angle is measured counter-clockwise from  the  X  axis
63       and  the  positive sense of the curve is assumed to be that moving from
64       point 0 to point n-1. A value for sl1 may be omitted  as  indicated  by
65       the switch sf1.
66
67       The  value  for  parameter  sln is in radians and contains the slope at
68       (x[n-1],y[n-1]). The angle is measured  counter-clockwise  from  the  X
69       axis  and  the positive sense of the curve is assumed to be that moving
70       from point 0 to point n-1. A value for sln may be omitted as  indicated
71       by the switch sf1.
72
73       The value of sf1 controls whether to use the values for sl1 and sln, or
74       compute those values internally.  Specifically, sf1
75
76       = 0 if sl1 and sln are user-specified.
77       = 1 if sl1 is user-specified, but sln is internally calculated.
78       = 2 if sln is user-specified, but sl1 is internally calculated.
79       = 3 if sl1 and sln are internally calculated.
80
81

ACCESS

83       To use c_ftkurv, load the NCAR Graphics library ngmath.
84

SEE ALSO

86       fitgrid_params, c_ftseti, c_ftsetr, c_ftsetc.
87
88       Complete documentation for Fitgrid is available at URL
89       http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html
90
92       Copyright (C) 2000
93       University Corporation for Atmospheric Research
94
95       The use of this Software is governed by a License Agreement.
96
97
98
99UNIX                              March 1998                  c_ftkurv(3NCARG)
Impressum