1c_csa3s(3NCARG)                  NCAR GRAPHICS                 c_csa3s(3NCARG)
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NAME

6       c_csa3s  -  cubic  spline  approximation, simple entry for three-dimen‐
7       sional input, gridded output
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FUNCTION PROTOTYPE

10       float *c_csa3s(int, float [], float [], float [], float [], int [], int, int,
11                      int, float [], float [], float [], int *);
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SYNOPSIS

15       float *c_csa3s (int n, float xi[], float yi[], float zi[],
16                       float ui[], int knots[3], int nxo, int nyo,
17                       int nzo, float xo[], float yo[], float zo[],
18                       int *ier);
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DESCRIPTION

22       n           (integer,input) The number of input data points. It must be
23                   that  n  is  greater  than  3 and, depending on the size of
24                   knots below, n may have to be larger.
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26       xi          (real, input) An array dimensioned for n containing  the  X
27                   coordinate values for the input function.
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29       yi          (real,  input)  An array dimensioned for n containing the Y
30                   coordinate values for the input function.
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32       zi          (real, input) An array dimensioned for n containing  the  Z
33                   coordinate values for the input function.
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35       ui          (real,  input) An array containing the functional values of
36                   the input function -- ui[k]  is  the  functional  value  at
37                   (xi[k], yi[k], zi[k]) for k=0,n-1.
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39       knots       (integer,  input)  The  number  of knots to be used in con‐
40                   structing the approximation spline. knots[0], knots[1]  and
41                   knots[2]  must each be at least 4. The larger the value for
42                   knots, the closer the approximated curve will come to pass‐
43                   ing through the input function values.
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45       nxo         (integer,  input)  The  number of X coordinate values to be
46                   calculated for the output surface.
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48       nyo         (integer, input) The number of Y coordinate  values  to  be
49                   calculated for the output surface.
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51       nzo         The  number of Z coordinate values to be calculated for the
52                   output grid.
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54       xo          (real, input) An array dimensioned for nxo containing the X
55                   coordinates of the output grid.
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57       yo          (real,  output) An array dimensioned for nyo containing the
58                   Y coordinates of the output grid.
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60       zo          (real, output) An array dimensioned for nzo containing  the
61                   Z coordinates of the output grid.
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63       ier         (pointer  to  integer,  output)  An error return value.  If
64                   *ier is returned as 0, then no  errors  were  detected.  If
65                   *ier is non-zero, then refer to the error list in the error
66                   table for details.
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USAGE

69       c_csa3s is called to find an  approximating  cubic  spline  for  three-
70       dimensional  input  data.  If you want to weight the input data values,
71       calculate derivatives, or handle data sparse areas specially, then  you
72       will need to use c_csa3xs.
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74       c_csa3s returns a pointer to a linear array of data that is the approx‐
75       imation spline stored in row-major order. That is, if out  is  declared
76       as
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78         float *out;
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80       and we set:
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82         out = c_csa3s(n, x, y, z, u, nx, ny, nz, xo, yo, zo, &ier);
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84       then  out[nz*ny*i  +  nz*j  + k] is the approximation function value at
85       coordinate point (xo[i], yo[j], zo[k]) for 0 <= i < nx, 0 <=  j  <  ny,
86       and 0 <= k < nz. The space for out is allocated internal to c_csa3s and
87       is nx*ny*nz floats in size.
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ACCESS

90       To use c_csa3s, load the NCAR Graphics library ngmath.
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SEE ALSO

93       csagrid, c_csa3xs, c_csa3ls, c_csa3lxs
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95       Complete documentation for Csagrid is available at URL
96       http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
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99       Copyright (C) 2000
100       University Corporation for Atmospheric Research
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102       This documentation is free software; you  can  redistribute  it  and/or
103       modify  it  under  the  terms of the GNU General Public License as pub‐
104       lished by the  Free  Software  Foundation;  either  version  2  of  the
105       License, or (at your option) any later version.
106
107       This  software  is  distributed in the hope that it will be useful, but
108       WITHOUT ANY  WARRANTY;  without  even  the  implied  warranty  of  MER‐
109       CHANTABILITY  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
110       Public License for more details.
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112       You should have received a copy of the GNU General Public License along
113       with  this  software;  if  not,  write to the Free Software Foundation,
114       Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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119UNIX                             January 1999                  c_csa3s(3NCARG)
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