1c_csa3xs(3NCARG) NCAR GRAPHICS c_csa3xs(3NCARG)
2
6 c_csa3xs - cubic spline approximation, expanded entry for three-dimen‐
7 sional input, gridded output
8
10 loat *c_csa3xs(int, float [], float [], float [], float [], float [],
11 int [], float, int [], int, int, int, float [],
12 float [], float [], int *);
13
16 float *c_csa3xs (int n, float xi[], float yi[], float zi[],
17 float ui[], float wts[], int knots[3], float smth,
18 int nderiv[3], int nxo, int nyo,
19 int nzo, float xo[], float yo[], float zo[],
20 int *ier);
21
24 n (integer,input) The number of input data points. It must be
25 that n is greater than 3 and, depending on the size of
26 knots below, n may have to be larger.
27 xi (real, input) An array dimensioned for n containing the X
29 coordinate values for the input function.
30 yi (real, input) An array dimensioned for n containing the Y
32 coordinate values for the input function.
33 zi (real, input) An array dimensioned for n containing the Z
35 coordinate values for the input function.
36 ui (real, input) An array containing the functional values of
38 the input function -- ui[k] is the functional value at
39 (xi[k], yi[k], zi[k]) for k=0,n-1.
40 wts (real, input) An array containing weights for the ui values
42 at the input values, that is, wts[l] is a weight for the
43 value of ui[l] for l=0,n-1. If you do not desire to weight
44 the input ui values, then set wts[0] to -1. The weights in
45 the wts array are relative and may be set to any non-nega‐
46 tive value. When c_csa3xs is called, the weights are summed
47 and the individual weights are normalized so that the
48 weight sum is unity.
49 knots (integer, input) The number of knots to be used in con‐
51 structing the approximation spline. knots[0], knots[1] and
52 knots[2] must each be at least 4. The larger the value for
53 knots, the closer the approximated curve will come to pass‐
54 ing through the input function values.
55 smth (real, input) A parameter that controls extrapolation into
57 data sparse regions. If smth is zero, then nothing special
58 is done in data sparse regions. A good first choice for
59 smth is 1.
60 nderiv (integer, input) For each of the two coordinate direction,
62 specifies whether you want functional values (nderiv=0),
63 first derivative values (nderiv=1), or second derivative
64 values (nderiv=2). For example, if nderiv[0]=1 and
65 nderiv[1]=1, then the second order mixed partial would be
66 computed.
67 nxo (integer, input) The number of X coordinate values to be
69 calculated for the output spline.
70 nyo (integer, input) The number of Y coordinate values to be
72 calculated for the output spline.
73 nzo (integer, input) The number of Z coordinate values to be
75 calculated for the output spline.
76 xo (real, input) An array dimensioned for nxo containing the X
78 coordinates of the output spline.
79 yo (real, output) An array dimensioned for nyo containing the
81 Y coordinates of the output spline.
82 zo (real, output) An array dimensioned for nzo containing the
84 Z coordinates of the output spline.
85 ier (pointer to integer, output) An error return value. If
87 *ier is returned as 0, then no errors were detected. If
88 *ier is non-zero, then refer to the error list in the error
89 table for details.
90
92 c_csa3xs is called to find an approximating cubic spline for three-
93 dimensional input data. c_csa3xs is called if you want to weight the
94 input data values, calculate derivatives, or handle data sparse areas
95 specially. If you do not want to do any of these three things, then use
96 c_csa3s.
97 c_csa3xs returns a pointer to a linear array of data that is the
99 approximation spline stored in row-major order. That is, if out is
100 declared as
101 float *out;
102 and we set:
104 out = c_csa3xs(ni, xi, yi, zi, ui, wts, knots, smth, nderiv,
106 nx, ny, nz, xo, yo, zo, &ier)
107 then out[nz*ny*i + nz*j + k] is the approximation function value at
108 coordinate point (xo[i], yo[j], zo[k]) for 0 <= i < nx, 0 <= j < ny,
109 and 0 <= k < nz. The space for out is allocated internal to c_csa3xs
110 and is nx*ny*nz floats in size.
111
114 To use c_csa3xs, load the NCAR Graphics library ngmath.
115
117 csagrid, c_csa3s, c_csa3ls, c_csa3lxs
118 Complete documentation for Csagrid is available at URL
120 http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
121
123 Copyright (C) 2000
124 University Corporation for Atmospheric Research
125 The use of this Software is governed by a License Agreement.
127UNIX January 1999 c_csa3xs(3NCARG)