1c_ftkurv(3NCARG) NCAR GRAPHICS c_ftkurv(3NCARG)
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6 c_ftkurv - interpolation for parametric curves
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9 int c_ftkurv (int, float [], float [], int, float [], float [], float
10 []);
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13 int c_ftkurv (n, xi, yi, m, t, xo, yo);
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16 n The number of input data values. (n > 1)
17 xi An array containing the abscissae for the input function.
19 yi An array containing the functional values (y[k] is the
21 functional value at x[k] for k=0,n-1).
22 m The number of desired interpolated values.
24 t Contains an array of values for the parameter mapping onto
26 the interpolated curve.
27 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 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.
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35 c_ftkurv returns an error value as per:
36 = 0 -- no error.
38 = 1 -- if n is less than 2.
39 = 2 -- if adjacent coordinate pairs coincide.
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42 This function calculates an interpolatory spline under tension through
43 a sequence of points in the plane.
44 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 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 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 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 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 The value of sf1 controls whether to use the values for sl1 and sln, or
74 compute those values internally. Specifically, sf1
75 = 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.
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83 To use c_ftkurv, load the NCAR Graphics library ngmath.
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86 fitgrid_params, c_ftseti, c_ftsetr, c_ftsetc.
87 Complete documentation for Fitgrid is available at URL
89 http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html
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92 Copyright (C) 2000
93 University Corporation for Atmospheric Research
94 The use of this Software is governed by a License Agreement.
96UNIX March 1998 c_ftkurv(3NCARG)