NAME

       c_csa2s  -  cubic  spline  approximation,  simple entry for two-dimensional input, gridded
       output

FUNCTION PROTOTYPE

       float *c_csa2s(int, float [], float [], float [], int [],
                      int, int, float [], float [], int *);

SYNOPSIS

       int c_csa2s(int n, float xi[], float yi[], float zi[], int knots[2],
                   int no, int mo, float xo[], float yo[], 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 containing the functional values of the input function
                   -- zi[k] is the functional value at (xi[k], yi[k]) for k=0,n-1.

       knots       (integer, input) The number of knots to be used in each  coordinate  direction
                   in  constructing  the  approximation spline.  knots[0] and knots[1] 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 coordinate values to be calculated for the
                   output surface.

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

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

       yo          (real, output) An array dimensioned for mo containing the Y 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_csa2s  is called to find an approximating cubic spline surface for two-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_csa2xs.

       c_csa2s  returns  a pointer to a linear array of data that is the approximated grid stored
       in row-major order. That is, if out is declared as

         float *out;

       and we set:

         out = c_csa2s(n, x, y, z, knots, no, mo, xo, yo, &ier);

       then out[i*mo+j] is the approximated function value at coordinate point (xo[i], yo[j]) for
       0  <= i < no and 0 <= j < mo. The space for out is allocated internal to c_csa2s and is no
       * mo floats in size.

ACCESS

       To use c_csa2s, load the NCAR Graphics library ngmath.

SEE ALSO

       csagrid, c_csa2xs, c_csa2ls, c_csa2lxs

       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.