1c_csa3lxs(3NCARG) NCAR GRAPHICS c_csa3lxs(3NCARG)
2
6 c_csa3lxs - cubic spline approximation, expanded entry for three-dimen‐
7 sional input, list output
8
10 float *c_csa3lxs(int, float [], float [], float [], float [],
11 float [], int [], float, int [],
12 int, float [], float [], float [], int *);
13
16 float *c_csa3lxs(int n, float xi[], float yi[], float zi[], float ui[],
17 float wts[], int knots[3], float smth, int nderiv[3],
18 int no, float xo[], float yo[], float zo[], int *ier);
19
22 n (integer,input) The number of input data points. It must be
23 that n is greater than 3 and, depending on the size of
24 knots below, n may have to be larger.
25 xi (real, input) An array dimensioned for n containing the X
27 coordinate values for the input function.
28 yi (real, input) An array dimensioned for n containing the Y
30 coordinate values for the input function.
31 zi (real, input) An array dimensioned for n containing the Z
33 coordinate values for the input function.
34 ui (real, input) An array containing the functional values of
36 the input function -- ui[k] is the functional value at
37 (xi[k], yi[k], zi[k]) for k=0,n-1.
38 wts (real, input) An array containing weights for the ui values
40 at the input values, that is, wts[l] is a weight for the
41 value of ui[l] for l=0,n-1. If you do not desire to weight
42 the input ui values, then set wts[0] to -1. The weights in
43 the wts array are relative and may be set to any non-nega‐
44 tive value. When c_csa3lxs is called, the weights are
45 summed and the individual weights are normalized so that
46 the weight sum is unity.
47 knots (integer, input) The number of knots to be used in con‐
49 structing the approximation spline. knots[0], knots[1],
50 and knots[2] must be at least 4. The larger the value for
51 knots, the closer the approximated curve will come to pass‐
52 ing through the input function values.
53 smth (real, input) A parameter that controls extrapolation into
55 data sparse regions. If smth is zero, then nothing special
56 is done in data sparse regions. A good first choice for
57 smth is 1.
58 nderiv (real, input) For each of the two coordinate direction,
60 specifies whether you want functional values (nderiv=0),
61 first derivative values (nderiv=1), or second derivative
62 values (nderiv=2). For example, if nderiv[0]=1, nderiv[1]=1
63 and nderiv[2]=0, then the second order mixed partial with
64 respect to X and Y would be computed.
65 no (integer, input) The number of X - Y - Z coordinate values
67 to be calculated for the output array.
68 xo (real, input) An array dimensioned for no containing the X
70 coordinates of the output list.
71 yo (real, output) An array dimensioned for no containing the Y
73 coordinates of the output list.
74 zo (real, output) An array dimensioned for no containing the Z
76 coordinates of the output list.
77 ier (pointer to integer, output) An error return value. If *ier
79 is returned as 0, then no errors were detected. If *ier is
80 non-zero, then refer to the error list in the error table
81 for details.
82
84 c_csa3lxs is called to find values of an approximating cubic spline at
85 specified three-dimensional coordinates. c_csa3lxs is called if you
86 want to weight the input data values, calculate derivatives, or handle
87 data sparse areas specially. If you do not want to do any of these
88 three things, then use c_csa3ls.
89 c_csa3lxs returns a pointer to a linear array of data that contains the
91 approximated values calculated at the input list of coordinate values.
92 That is, if out is declared as
93 float *out;
95 and we set:
97 out = c_csa3lxs(n, x, y, z, u, wts, knots, smth, nderiv,
99 no, xo, yo, zo, &ier);
100 then out[i] is the approximated function value at coordinate point
102 (xo[i], yo[i], zo[i]) for 0 <= i < no. The space for out is allocated
103 internal to c_csa3lxs and is no floats in size.
104
106 To use c_csa3lxs, load the NCAR Graphics library ngmath.
107
109 csagrid, c_csa3s, c_csa3xs, c_csa3lxs
110 Complete documentation for Csagrid is available at URL
112 http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
113
115 Copyright (C) 2000
116 University Corporation for Atmospheric Research
117 This documentation is free software; you can redistribute it and/or
119 modify it under the terms of the GNU General Public License as pub‐
120 lished by the Free Software Foundation; either version 2 of the
121 License, or (at your option) any later version.
122 This software is distributed in the hope that it will be useful, but
124 WITHOUT ANY WARRANTY; without even the implied warranty of MER‐
125 CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
126 Public License for more details.
127 You should have received a copy of the GNU General Public License along
129 with this software; if not, write to the Free Software Foundation,
130 Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
131UNIX January 1999 c_csa3lxs(3NCARG)