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

6       KURVD - interpolation and derivatives for parametric curves
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SYNOPSIS

9       CALL KURVD (T, XS, YS, XST, YST, XSTT, YSTT, N, X, Y, XP, YP, S, SIGMA)
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11       This  subroutine  behaves like KURV2 except that in addition it returns
12       the first and second derivatives of  the  component  functions  in  the
13       parameterization.  The interval [0.,1.] maps onto a curve in the plane.
14       The resulting curve has a parametric representation both of whose  com‐
15       ponents  are  splines  under tension and functions of the polygonal arc
16       length. KURV1 must be called before calling KURVD.
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DESCRIPTION

19       T           (real,input) A value to be mapped to a point on the  curve.
20                   The  interval [0.,1.] is mapped onto the curve such that 0.
21                   is mapped to (X(1),Y(1)) and 1. is mapped  to  (X(N),Y(N)).
22                   Values outside of [0.,1.] result in extrapolation.
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24       XS          (real,output) Contains the X coordinate of the point that T
25                   maps to.
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27       YS          (real,output) Contains the Y coordinate of the point that T
28                   maps to.
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30       XST         (real,output)  Contains the first derivatives of the X com‐
31                   ponent with respect to T.
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33       YST         (real,output) Contains the first derivatives of the Y  com‐
34                   ponent with respect to T.
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36       XSTT        (real,output) Contains the second derivatives of the X com‐
37                   ponent with respect to T.
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39       YSTT        (real,output) Contains the second derivatives of the X com‐
40                   ponent with respect to T.
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42       N           (integer,input) The number of input data points. (N > 1)
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44       X           (real,input)  An array containing the X values of the input
45                   points.
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47       Y           (real,input) An array containing the Y values of the  input
48                   points. Adjacent pairs of points must be distinct.
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50       XP          (real,input) An array of length N as computed by KURV1.
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52       YP          (real,input) An array of length N as computed by KURV1.
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54       S           (real,input)  An array of length N containing the polygonal
55                   arc lengths of the curve, as computed by KURV1.
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57       SIGMA       (real,input) Tension factor. Values near zero result  in  a
58                   cubic  spline;  large  values  (e.g. 50) result in nearly a
59                   polygonal line. A typical value is 1.
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ACCESS

62       To use KURVD, load the NCAR Graphics library ngmath.
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SEE ALSO

65       kurv1,kurv2, fitgrid_params.
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67       Complete documentation for Fitgrid is available at URL
68       http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html
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71       Copyright (C) 2000
72       University Corporation for Atmospheric Research
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74       The use of this Software is governed by a License Agreement.
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78UNIX                              March 1998                     KURVD(3NCARG)
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