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

NAME

6       KURVD - interpolation and derivatives for parametric curves
7

SYNOPSIS

9       CALL KURVD (T, XS, YS, XST, YST, XSTT, YSTT, N, X, Y, XP, YP, S, SIGMA)
10
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.
17

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.
23
24       XS          (real,output) Contains the X coordinate of the point that T
25                   maps to.
26
27       YS          (real,output) Contains the Y coordinate of the point that T
28                   maps to.
29
30       XST         (real,output)  Contains the first derivatives of the X com‐
31                   ponent with respect to T.
32
33       YST         (real,output) Contains the first derivatives of the Y  com‐
34                   ponent with respect to T.
35
36       XSTT        (real,output) Contains the second derivatives of the X com‐
37                   ponent with respect to T.
38
39       YSTT        (real,output) Contains the second derivatives of the X com‐
40                   ponent with respect to T.
41
42       N           (integer,input) The number of input data points. (N > 1)
43
44       X           (real,input)  An array containing the X values of the input
45                   points.
46
47       Y           (real,input) An array containing the Y values of the  input
48                   points. Adjacent pairs of points must be distinct.
49
50       XP          (real,input) An array of length N as computed by KURV1.
51
52       YP          (real,input) An array of length N as computed by KURV1.
53
54       S           (real,input)  An array of length N containing the polygonal
55                   arc lengths of the curve, as computed by KURV1.
56
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.
60

ACCESS

62       To use KURVD, load the NCAR Graphics library ngmath.
63

SEE ALSO

65       kurv1,kurv2, fitgrid_params.
66
67       Complete documentation for Fitgrid is available at URL
68       http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html
69

71       Copyright (C) 2000
72       University Corporation for Atmospheric Research
73
74       This documentation is free software; you  can  redistribute  it  and/or
75       modify  it  under  the  terms of the GNU General Public License as pub‐
76       lished by the  Free  Software  Foundation;  either  version  2  of  the
77       License, or (at your option) any later version.
78
79       This  software  is  distributed in the hope that it will be useful, but
80       WITHOUT ANY  WARRANTY;  without  even  the  implied  warranty  of  MER‐
81       CHANTABILITY  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
82       Public License for more details.
83
84       You should have received a copy of the GNU General Public License along
85       with  this  software;  if  not,  write to the Free Software Foundation,
86       Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
87
88
89
90
91UNIX                              March 1998                     KURVD(3NCARG)
Impressum