NAME

       c_csa3ls  -  cubic  spline  approximation,  simple entry for three-dimensional input, list
       output

FUNCTION PROTOTYPE

       float *c_csa3ls(int, float [], float [], float [], float [],
                       int [], int, float [], float [], float[], int *);

SYNOPSIS

       float *c_csa3ls(int n, float xi[], float yi[], float zi[], float ui[],
                       int knots[3], int no, float xo[], float yo[], float zo[],
                       int *);

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 be  at  least  4.
                   The larger the value for knots, the closer the approximated curve will come to
                   passing through the input function values.

       no          (integer, input) The number of X - Y coordinate values to  be  calculated  for
                   the output array.

       xo          (real,  input) An array dimensioned for no containing the X coordinates of the
                   output list.

       yo          (real, output) An array dimensioned for no containing the Y coordinates of the
                   output list.

       zo          (real, output) An array dimensioned for no containing the Z coordinates of the
                   output list.

       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_csa3ls is called to find values of an approximating cubic  spline  at  specified  three-
       dimensional  coordinates.   If  you  want  to  weight  the  input  data  values, calculate
       derivatives, or handle data sparse areas specially, then you will need to use c_csa3lxs.

       c_csa3ls returns a pointer to a linear array of data that contains the approximated values
       calculated at the input list of coordinate values. That is, if out is declared as

         float *out;

       and we set:

         out = c_csa3ls(n, x, y, z, u, knots, no, xo, yo, zo, &ier);

       then  out[i]  is the approximated function value at coordinate point (xo[i], yo[i], zo[i])
       for 0 <= i < no. The space for out is allocated internal to c_csa3ls and is no  floats  in
       size.

ACCESS

       To use c_csa3ls, load the NCAR Graphics library ngmath.

SEE ALSO

       csagrid, c_csa3s, c_csa3xs, 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.