NAME

       c_csa3s - cubic spline approximation, simple entry for three-dimensional input, gridded output

FUNCTION PROTOTYPE

       float *c_csa3s(int, float [], float [], float [], float [], int [], int, int,
                      int, float [], float [], float [], int *);

SYNOPSIS

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

DESCRIPTION

       n           (integer,input)  The  number  of  input data points. It must be that n is greater than 3 and,
                   depending on the size of knots below, n may have to be larger.

       xi          (real, input) An array dimensioned for n containing the X coordinate  values  for  the  input
                   function.

       yi          (real,  input)  An  array  dimensioned for n containing the Y coordinate values for the input
                   function.

       zi          (real, input) An array dimensioned for n containing the Z coordinate  values  for  the  input
                   function.

       ui          (real, input) An array containing the functional values of the input function -- ui[k] is the
                   functional value at (xi[k], yi[k], zi[k]) for k=0,n-1.

       knots       (integer,  input)  The  number  of knots to be used in constructing the approximation spline.
                   knots[0], knots[1] and knots[2] must each be at least 4. The larger the value for knots,  the
                   closer the approximated curve will come to passing through the input function values.

       nxo         (integer, input) The number of X coordinate values to be calculated for the output surface.

       nyo         (integer, input) The number of Y coordinate values to be calculated for the output surface.

       nzo         The number of Z coordinate values to be calculated for the output grid.

       xo          (real, input) An array dimensioned for nxo containing the X coordinates of the output grid.

       yo          (real, output) An array dimensioned for nyo containing the Y coordinates of the output grid.

       zo          (real, output) An array dimensioned for nzo containing the Z coordinates of the output grid.

       ier         (pointer to integer, output) An error return value.  If *ier is returned as 0, then no errors
                   were  detected.  If  *ier  is  non-zero,  then refer to the error list in the error table for
                   details.

USAGE

       c_csa3s is called to find an approximating cubic spline for three-dimensional input data. If you want  to
       weight the input data values, calculate derivatives, or handle data sparse areas specially, then you will
       need to use c_csa3xs.

       c_csa3s  returns a pointer to a linear array of data that is the approximation spline stored in row-major
       order. That is, if out is declared as

         float *out;

       and we set:

         out = c_csa3s(n, x, y, z, u, nx, ny, nz, xo, yo, zo, &ier);

       then out[nz*ny*i + nz*j + k] is the approximation function  value  at  coordinate  point  (xo[i],  yo[j],
       zo[k])  for 0 <= i < nx, 0 <= j < ny, and 0 <= k < nz. The space for out is allocated internal to c_csa3s
       and is nx*ny*nz floats in size.

ACCESS

       To use c_csa3s, load the NCAR Graphics library ngmath.

SEE ALSO

       csagrid, c_csa3xs, c_csa3ls, c_csa3lxs

       Complete documentation for Csagrid is available at URL
       http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html

COPYRIGHT

       Copyright (C) 2000
       University Corporation for Atmospheric Research

       The use of this Software is governed by a License Agreement.

UNIX                                              January 1999                                   c_csa3s(3NCARG)