1c_csa1xs(3NCARG) NCAR GRAPHICS c_csa1xs(3NCARG)
2
6 c_csa1xs - cubic spline approximation, expanded entry for one-dimen‐
7 sional input
8
10 float *c_csa1xs(int, float [], float [], float [], int,
11 float, int, int, float [], int *);
12
15 float *c_csa1xs(int n, float xi[], float yi[], float wts[],
16 int knots, float smth, int nderiv,
17 int m, float xo[], int *ier);
18
21 n (integer,input) The number of input data points. It must be
22 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
26 abscissae for the input function.
27 yi (real, input) An array dimensioned for n containing the
29 functional values of the input function -- yi[k] is the
30 functional value at xi[k] for k=0,n-1.
31 wts (real, input) An array dimensioned for n containing weights
33 for the yi values at the input xi values, that is, wts[l]
34 is a weight for the value of yi[l] for l=0,n-1. If you do
35 not desire to weight the input yi values, then set wts[0]
36 to -1. The weights in the wts array are relative and may be
37 set to any non-negative value. When c_csa1xs is called,
38 the weights are summed and the individual weights are nor‐
39 malized so that the weight sum is unity.
40 knots (integer, input) The number of knots to be used in con‐
42 structing the approximation spline. knots must be at least
43 4. The larger the value for knots, the closer the approxi‐
44 mated curve will come to passing through the input function
45 values.
46 smth (real, input) A parameter that controls extrapolation into
48 data sparse regions. If smth is zero, then nothing special
49 is done in data sparse regions. A good first choice for
50 smth is 1.
51 nderiv (integer, input) Specifies whether you want functional val‐
53 ues (nderiv=0), first derivative values (nderiv=1), or sec‐
54 ond derivative values (nderiv=2).
55 m (integer, input) The number of values to be calculated for
57 the output curve.
58 xo (real, input) An array dimensioned for m containing the X
60 coordinates of the output curve.
61 ier (pointer to integer, output) An error return value. If *ier
63 is returned as 0, then no errors were detected. If *ier is
64 non-zero, then refer to the error list in the error table
65 for details.
66
68 c_csa1xs is called to find an approximating cubic spline for one-dimen‐
69 sional input data. c_csa1xs is called if you want to weight the input
70 data values, calculate derivatives, or handle data sparse areas spe‐
71 cially. If you do not want to do any of these three things, then use
72 c_csa1s.
73 c_csa1s returns a pointer to a linear array of data that is the approx‐
75 imated curve.
76
78 To use c_csa1xs, load the NCAR Graphics library ngmath.
79
81 csagrid, c_csa1s, c_csa1ls, c_csa1lxs
82 Complete documentation for Csagrid is available at URL
84 http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
85
87 Copyright (C) 2000
88 University Corporation for Atmospheric Research
89 The use of this Software is governed by a License Agreement.
91UNIX January 1999 c_csa1xs(3NCARG)