1c_csa2s(3NCARG)                  NCAR GRAPHICS                 c_csa2s(3NCARG)
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NAME

6       c_csa2s  - cubic spline approximation, simple entry for two-dimensional
7       input, gridded output
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FUNCTION PROTOTYPE

10       float *c_csa2s(int, float [], float [], float [], int [],
11                      int, int, float [], float [], int *);
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SYNOPSIS

15       int c_csa2s(int n, float xi[], float yi[], float zi[], int knots[2],
16                   int no, int mo, float xo[], float yo[], int *ier);
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DESCRIPTION

20       n           (integer,input) The number of input data points. It must be
21                   that  n  is  greater  than  3 and, depending on the size of
22                   knots below, n may have to be larger.
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24       xi          (real, input) An array dimensioned for n containing  the  X
25                   coordinate values for the input function.
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27       yi          (real,  input)  An array dimensioned for n containing the Y
28                   coordinate values for the input function.
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30       zi          (real, input) An array containing the functional values  of
31                   the  input  function  --  zi[k]  is the functional value at
32                   (xi[k], yi[k]) for k=0,n-1.
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34       knots       (integer, input) The number of knots to  be  used  in  each
35                   coordinate  direction  in  constructing  the  approximation
36                   spline.  knots[0] and knots[1] must  be  at  least  4.  The
37                   larger  the  value  for  knots, the closer the approximated
38                   curve will come to passing through the input function  val‐
39                   ues.
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41       no          (integer,  input)  The  number of X coordinate values to be
42                   calculated for the output surface.
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44       mo          (integer, input) The number of Y coordinate  values  to  be
45                   calculated for the output surface.
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47       xo          (real,  input) An array dimensioned for no containing the X
48                   coordinates of the output grid.
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50       yo          (real, output) An array dimensioned for mo containing the Y
51                   coordinates of the output grid.
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53       ier         (pointer to integer, output) An error return value. If *ier
54                   is returned as 0, then no errors were detected. If *ier  is
55                   non-zero,  then  refer to the error list in the error table
56                   for details.
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USAGE

59       c_csa2s is called to find an approximating  cubic  spline  surface  for
60       two-dimensional  input  data. If you want to weight the input data val‐
61       ues, calculate derivatives, or handle data sparse areas specially, then
62       you will need to use c_csa2xs.
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64       c_csa2s returns a pointer to a linear array of data that is the approx‐
65       imated grid stored in row-major order. That is, if out is declared as
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67         float *out;
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69       and we set:
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71         out = c_csa2s(n, x, y, z, knots, no, mo, xo, yo, &ier);
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73       then out[i*mo+j] is the approximated function value at coordinate point
74       (xo[i],  yo[j])  for  0 <= i < no and 0 <= j < mo. The space for out is
75       allocated internal to c_csa2s and is no * mo floats in size.
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ACCESS

78       To use c_csa2s, load the NCAR Graphics library ngmath.
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SEE ALSO

81       csagrid, c_csa2xs, c_csa2ls, c_csa2lxs
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83       Complete documentation for Csagrid is available at URL
84       http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
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87       Copyright (C) 2000
88       University Corporation for Atmospheric Research
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90       This documentation is free software; you  can  redistribute  it  and/or
91       modify  it  under  the  terms of the GNU General Public License as pub‐
92       lished by the  Free  Software  Foundation;  either  version  2  of  the
93       License, or (at your option) any later version.
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95       This  software  is  distributed in the hope that it will be useful, but
96       WITHOUT ANY  WARRANTY;  without  even  the  implied  warranty  of  MER‐
97       CHANTABILITY  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
98       Public License for more details.
99
100       You should have received a copy of the GNU General Public License along
101       with  this  software;  if  not,  write to the Free Software Foundation,
102       Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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107UNIX                             January 1999                  c_csa2s(3NCARG)
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