1c_csa1xs(3NCARG)                 NCAR GRAPHICS                c_csa1xs(3NCARG)
2
3
4

NAME

6       c_csa1xs  -  cubic  spline approximation, expanded entry for one-dimen‐
7       sional input
8

FUNCTION PROTOTYPE

10       float *c_csa1xs(int, float [], float [], float [], int,
11                    float, int, int, float [], int *);
12
13

SYNOPSIS

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
19

DESCRIPTION

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
25       xi          (real, input) An array dimensioned  for  n  containing  the
26                   abscissae for the input function.
27
28       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
32       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
41       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
47       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
52       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
56       m           (integer,  input) The number of values to be calculated for
57                   the output curve.
58
59       xo          (real, input) An array dimensioned for m containing  the  X
60                   coordinates of the output curve.
61
62       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

USAGE

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
74       c_csa1s returns a pointer to a linear array of data that is the approx‐
75       imated curve.
76

ACCESS

78       To use c_csa1xs, load the NCAR Graphics library ngmath.
79

SEE ALSO

81       csagrid, c_csa1s, c_csa1ls, c_csa1lxs
82
83       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
90       The use of this Software is governed by a License Agreement.
91
92
93
94UNIX                             January 1999                 c_csa1xs(3NCARG)
Impressum