1c_csa2lxs(3NCARG) NCAR GRAPHICS c_csa2lxs(3NCARG)
2
6 c_csa2lxs - cubic spline approximation, expanded entry for two-dimen‐
7 sional input, list output
8
10 float *c_csa2lxs(int, float [], float [], float [], float [], int [],
11 float, int [], int, float [], float [], int *);
12
15 int c_csa2lxs(int n, float xi[], float yi[], float zi[],
16 float wts[], int knots[2], float smth, int nderiv[2],
17 int no, float xo[], float yo[], int *ier);
18
21 n (integer, input) The number of input data points. It must
22 be that n is greater than 3 and, depending on the size of
23 knots below, n may have to be larger.
24 xi (real, input) An array dimensioned for n containing the X
26 coordinate values for the input function.
27 yi (real, input) An array dimensioned for n containing the Y
29 coordinate values for the input function.
30 zi (real, input) An array containing the functional values of
32 the input function -- zi[k] is the functional value at
33 (xi[k], yi[k]) for k=0,n-1.
34 wts (real, input) An array containing weights for the zi values
36 at the input xi and yi values, that is, wts[l] is a weight
37 for the value of zi[l] for l=0,n-1. If you do not desire to
38 weight the input zi values, then set wts[0] to -1. The
39 weights in the wts array are relative and may be set to any
40 non-negative value. When c_csa2lxs is called, the weights
41 are summed and the individual weights are normalized so
42 that the weight sum is unity.
43 knots (integer, input) The number of knots to be used in con‐
45 structing the approximation spline. knots[0] and knots[1]
46 must be at least 4. The larger the value for knots, the
47 closer the approximated curve will come to passing through
48 the input function values.
49 smth (real, input) A parameter that controls extrapolation into
51 data sparse regions. If smth is zero, then nothing special
52 is done in data sparse regions. A good first choice for
53 smth is 1.
54 nderiv (integer, input) For each of the two coordinate direction,
56 specifies whether you want functional values (nderiv=0),
57 first derivative values (nderiv=1), or second derivative
58 values (nderiv=2). For example, if nderiv[0]=1 and
59 nderiv[1]=1, then the second order mixed partial would be
60 computed.
61 no (integer, input) The number of X - Y coordinate values to
63 be calculated for the output array.
64 xo (real, input) An array dimensioned for no containing the X
66 coordinates of the output list.
67 yo (real, output) An array dimensioned for no containing the Y
69 coordinates of the output list.
70 ier (pointer to integer, output) An error return value. If
72 *ier is returned as 0, then no errors were detected. If
73 *ier is non-zero, then refer to the error list in the error
74 table for details.
75
77 c_csa2lxs is called to find values of an approximating cubic spline at
78 specified two-dimensional coordinates. If you want to weight the input
79 data values, calculate derivatives, or handle data sparse areas spe‐
80 cially, then you will need to use c_csa2lxs.
81 c_csa2lxs returns a pointer to a linear array of data that contains the
83 approximated values calculated at the input list of coordinate values.
84 That is, if out is declared as
85 float *out;
87 and we set:
89 out = c_csa2lxs(n, x, y, z, wts, knots, smth, nderiv, no, xo, yo, &ier);
91 then out[i] is the approximated function value at coordinate point
93 (xo[i], yo[i]) for 0 <= i < no. The space for out is allocated internal
94 to c_csa2lxs and is no floats in size.
95
97 To use c_csa2lxs, load the NCAR Graphics library ngmath.
98
100 csagrid, c_csa2s, c_csa2xs, c_csa2ls
101 Complete documentation for Csagrid is available at URL
103 http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
104
106 Copyright (C) 2000
107 University Corporation for Atmospheric Research
108 The use of this Software is governed by a License Agreement.
110UNIX January 1999 c_csa2lxs(3NCARG)