1KURV1(3NCARG)                    NCAR GRAPHICS                   KURV1(3NCARG)
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NAME

6       KURV1 - calculate values for KURV2 usage
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SYNOPSIS

9       CALL KURV1  (N, X, Y, SLP1, SLPN, ISLPSW, XP, YP, TEMP, S, SIGMA, IER)
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11       This  subroutine  calculates  certain  values that are used by KURV2 in
12       order to compute  an  interpolatory  spline  under  tension  through  a
13       sequence of points in the plane. The actual computation of the interpo‐
14       lated values must be done using KURV2.
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DESCRIPTION

17       N           (integer, input) The number of input data values. (N > 1)
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19       X           (real, input) An array  containing  the  X  values  of  the
20                   points.
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22       Y           (real,  input)  An  array  containing  the  Y values of the
23                   points.  Adjacent pairs of points must be distinct.
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25       SLP1        (real, input) A value (in radians) containing the slope  at
26                   (X(1),Y(1)).   The  angles  are  measured counter-clockwise
27                   from the X axis and the positive  sense  of  the  curve  is
28                   assumed  to be that moving from point 1 to point N. A value
29                   for SLP1 may be omitted as indicated by the switch ISLPSW.
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31       SLPN        (real, input) A value (in radians) containing the slope  at
32                   (X(N),Y(N)). The angles are measured counter-clockwise from
33                   the X axis and the positive sense of the curve  is  assumed
34                   to be that moving from point 1 to point N. A value for SLP2
35                   may be omitted as indicated by the switch ISLPSW.
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37       ISLPSW      (integer, input) A switch to indicate whether the slopes at
38                   the end points should be calculated internally.
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40                   = 0 if SLP1 and SLPN are user-specified.
41                   =  1  if SLP1 is user-specified, but SLPN calculated inter‐
42                   nally.
43                   = 2 if SLPN is user-specified, but SLP1  calculated  inter‐
44                   nally.
45                   = 3 if SLP1 and SLPN are internally calculated.
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47       XP          (real, output) An array of length N.
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49       YP          (real, output) An array of length N.
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51       TEMP        (real, input) Scratch space.
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53       S           (real,  input)  An array of length N. On output, S contains
54                   the polygonal arclengths of the curve.
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56       SIGMA       (real, input) Tension factor. Values near zero result in  a
57                   cubic  spline;  large  values  (e.g. 50) result in nearly a
58                   polygonal line. A typical value is 1.
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60       IER         (integer, output) An error return value. If IER is returned
61                   as 0, then no errors were detected.
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63                   = 1 if N is less than 2.
64                   = 2 if a pair of adjacent points coincide.
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ACCESS

67       To use KURV1, load the NCAR Graphics library ngmath.
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SEE ALSO

70       kurv2, fitgrid_params.
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72       Complete documentation for Fitgrid is available at URL
73       http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html
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76       Copyright (C) 2000
77       University Corporation for Atmospheric Research
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79       The use of this Software is governed by a License Agreement.
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83UNIX                              March 1998                     KURV1(3NCARG)
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