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

6       KURVPD - nterpolation and derivatives for closed  parametric curves
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SYNOPSIS

9       CALL  KURVPD  (T,  XS,  YS,  XST,  YST, XSTT, YSTT, N, X, Y, XP, YP, S,
10       SIGMA)
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12       This subroutine behaves like KURVP2 except that in addition it  returns
13       the  first  and  second  derivatives  of the component functions in the
14       parameterization. The interval [0.,1.] maps onto a closed curve in  the
15       plane.  The  resulting  curve  has  a parametric representation both of
16       whose components are splines under tension and functions of the polygo‐
17       nal arc length. KURVP1 must be called before calling KURVPD.
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DESCRIPTION

20       T           (real,input)  A value to be mapped to a point on the curve.
21                   The interval [0.,1.] is mapped onto the curve such that  0.
22                   is  mapped  to (X(1),Y(1)) and 1. is mapped to (X(1),Y(1)).
23                   Any interval [TT,TT+1.] maps onto the entire closed curve.
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25       XS          (real,output) Contains the X coordinate of the point that T
26                   maps to.
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28       YS          (real,output) Contains the Y coordinate of the point that T
29                   maps to.
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31       XST         (real,output) Contains the first derivatives of the X  com‐
32                   ponent with respect to T.
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34       YST         (real,output)  Contains the first derivatives of the Y com‐
35                   ponent with respect to T.
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37       XSTT        (real,output) Contains the second derivatives of the X com‐
38                   ponent with respect to T.
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40       YSTT        (real,output) Contains the second derivatives of the X com‐
41                   ponent with respect to T.
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43       N           (integer,input) The number of input data points. (N > 1)
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45       X           (real,input) An array containing the X values of the  input
46                   points.
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48       Y           (real,input)  An array containing the Y values of the input
49                   points. Adjacent pairs of points must be distinct.
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51       XP          (real,input) An array of length N as computed by KURVP1.
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53       YP          (real,input) An array of length N as computed by KURVP1.
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55       S           (real,input) An array of length N containing the  polygonal
56                   arc lengths of the curve, as computed by KURVP1.
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58       SIGMA       (real,input)  Tension  factor. Values near zero result in a
59                   cubic spline; large values (e.g. 50)  result  in  nearly  a
60                   polygonal line. A typical value is 1.
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ACCESS

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

66       kurvp1,kurvp2, fitgrid_params.
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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       This  documentation  is  free  software; you can redistribute it and/or
76       modify it under the terms of the GNU General  Public  License  as  pub‐
77       lished  by  the  Free  Software  Foundation;  either  version  2 of the
78       License, or (at your option) any later version.
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80       This software is distributed in the hope that it will  be  useful,  but
81       WITHOUT  ANY  WARRANTY;  without  even  the  implied  warranty  of MER‐
82       CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  General
83       Public License for more details.
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85       You should have received a copy of the GNU General Public License along
86       with this software; if not, write  to  the  Free  Software  Foundation,
87       Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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92UNIX                              March 1998                    KURVPD(3NCARG)
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