1CSA1XS(3NCARG) NCAR GRAPHICS CSA1XS(3NCARG)
2
6 CSA1XS - cubic spline approximation, expanded entry for one-dimensional
7 input
8
10 CALL CSA1XS (NI, XI, YI, WTS, KNOTS, SMTH, DERIV, NO, XO, YO, NWRK,
11 WORK, IER)
12
14 NI (integer,input) The number of input data points. It must be
15 that NI > 3 and, depending on the size of KNOTS below, NI
16 may have to be larger.
17 XI (real, input) An array dimensioned for NI containing the X
19 coordinates of the input data points.
20 YI (real, input) An array dimensioned for NI containing func‐
22 tion values at the input XI values, that is, YI(L) is the
23 value of the input function at XI(L) for L=1,NI.
24 WTS (real, input) An array dimensioned for NI containing
26 weights for the YI values at the input XI values, that is,
27 WTS(L) is a weight for the value of YI(L) for L=1,NI. If
28 you do not desire to weight the input YI values, then set
29 WTS(1) to -1. The weights in the WTS array are relative
30 and may be set to any non-negative value. When CSA1XS is
31 called, the weights are summed and the individual weights
32 are normalized so that the weight sum is unity.
33 KNOTS (integer, input) The number of knots to be used in con‐
35 structing the approximation spline. KNOTS must be at least
36 4. The larger the value for KNOTS, the closer the approxi‐
37 mated curve will come to passing through the input function
38 values.
39 SMTH (real, input) A parameter that controls extrapolation into
41 data sparse regions. If SMTH is zero, then nothing special
42 is done in data sparse regions. A good first choice for
43 SMTH is 1.
44 NDERIV (integer, input) Specifies whether you want functional val‐
46 ues (NDERIV=0), first derivative values (NDERIV=1), or sec‐
47 ond derivative values (NDERIV=2).
48 NO (integer, input) The number of values to be calculated for
50 the output curve.
51 XO (real, input) An array dimensioned for NO containing the X
53 coordinates of the output curve.
54 YO (real, output) An array dimensioned for NO containing the
56 calculated function values for the output curve.
57 NWRK (integer, input) The size of the WORK array. NWRK must be
59 at least KNOTS*(KNOTS+3).
60 WORK (real, input) A work array dimensioned for NWRK.
62 IER (integer, output) An error return value. If IER is
64 returned as 0, then no errors were detected. If IER is non-
65 zero, then refer to the man page for csagrid_errors for
66 details.
67
69 CSA1XS is called to find an approximating cubic spline for one-dimen‐
70 sional input data. CSA1XS is called if you want to weight the input
71 data values, calculate derivatives, or handle data sparse areas spe‐
72 cially. If you do not want to do any of these three things, then use
73 CSA1S.
74
76 To use CSA1XS, load the NCAR Graphics library ngmath.
77
79 csagrid, csa1s, csa1ls, csa1lxs
80 Complete documentation for Csagrid is available at URL
82 http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
83
85 Copyright (C) 2000
86 University Corporation for Atmospheric Research
87 This documentation is free software; you can redistribute it and/or
89 modify it under the terms of the GNU General Public License as pub‐
90 lished by the Free Software Foundation; either version 2 of the
91 License, or (at your option) any later version.
92 This software is distributed in the hope that it will be useful, but
94 WITHOUT ANY WARRANTY; without even the implied warranty of MER‐
95 CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
96 Public License for more details.
97 You should have received a copy of the GNU General Public License along
99 with this software; if not, write to the Free Software Foundation,
100 Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
101UNIX January 1999 CSA1XS(3NCARG)