1c_ftkurvp(3NCARG)                NCAR GRAPHICS               c_ftkurvp(3NCARG)
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NAME

6       c_ftkurvp - interpolation for closed parametric curves
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FUNCTION PROTOTYPE

9       int  c_ftkurvp (int, float [], float [], int, float [], float [], float
10       []);
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SYNOPSIS

13       int c_ftkurvp (n, xi, yi, m, t, xo, yo);
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DESCRIPTION

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

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

43       This procedure calculates an interpolatory spline under tension through
44       a sequence of points in the plane forming a closed curve.
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46       Given a  sequence  of  distinct  input  points  (  (x[0],y[0]),  ...  ,
47       (x[n-1],y[n-1]),  the  interpolated  curve  is parameterized by mapping
48       points in the interval [0.,1.] onto the interpolated curve. The result‐
49       ing  curve has a parametric representation both of whose components are
50       splines under tension and functions of the polygonal  arc  length.  The
51       value  0.  is  mapped  onto (x[0],y[0]) and the value 1. is mapped onto
52       (x[0],y[0]) as well (completing the closed curve).
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54       c_ftkurvp is called after all of the desired values for control parame‐
55       ters  have  been set using the procedures c_ftseti, c_ftsetr, c_ftsetc.
56       The only control parameter that applies to c_ftkurvp is: sig.
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58       The value for the parameter sig specifies the  tension  factor.  Values
59       near  zero  result  in a cubic spline; large values (e.g. 50) result in
60       nearly a polygonal line. A typical value is 1. (the default).
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ACCESS

63       To use c_ftkurvp, load the NCAR Graphics library ngmath.
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SEE ALSO

66       fitgrid_params, c_ftseti, c_ftsetr, c_ftsetc.
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68       Complete documentation for Fitgrid is available at URL
69       http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html
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72       Copyright (C) 2000
73       University Corporation for Atmospheric Research
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75       The use of this Software is governed by a License Agreement.
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79UNIX                              March 1998                 c_ftkurvp(3NCARG)
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