NAME

       CSA2S - cubic spline approximation, simple entry for two-dimensional input, gridded output

SYNOPSIS

       CALL CSA2S (NI, XI, UI, KNOTS, NXO, ,NYO, XO, YO, UO, NWRK, WORK, IER)

DESCRIPTION

       NI          (integer,input)  The  number  of  input data points. It must be that NI .gt. 3
                   and, depending on the size of KNOTS below, NI may have to be larger.

       XI          (real, input) An array containing the X - Y  coordinates  of  the  input  data
                   points. XI is dimensioned for 2 x NI.  XI(1,L) is the X coordinate and XI(2,L)
                   is the Y coordinate for the input domain for L=1,NI.

       UI          (real, input) An array dimensioned for NI containing function  values  at  the
                   input  XI  values,  that  is  UI(L)  is the value of the input function at the
                   coordinate (XI(1,L),XI(2,L)) for L=1,NI.

       KNOTS       (integer,  input)  The  number  of  knots  to  be  used  in  constructing  the
                   approximation  spline.   KNOTS is dimensioned for 2 and provides the number of
                   knots to be used in the X and the Y directions.  Both  KNOTS(1)  and  KNOTS(2)
                   must  be  at  least  4.   The  larger  the  values  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 in the output grid.

       NYO         (integer, input) The number of Y coordinate values in the output grid.

       XO          (real, input) An array dimensioned for NXO containing the X coordinates of the
                   output surface.

       YO          (real, input) An array dimensioned for NYO containing the Y coordinates of the
                   output surface.

       UO          (real, output) An array dimensioned for NXO x NYO  containing  the  calculated
                   function  values for the output surface.  UO(I,J) is the calculated functional
                   value at (XO(I),YO(J)) for I=1,NXO and J=1,NYO.

       NWRK        (integer, input)  The  size  of  the  WORK  array.   NWRK  must  be  at  least
                   KNOTS(1)*KNOTS(2)*(KNOTS(1)*KNOTS(2)+3).

       WORK        (real, input) A work array dimensioned for NWRK.

       IER         (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  man  page  for
                   csagrid_errors for details.

USAGE

       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 CSA2XS.

ACCESS

       To use CSA2S, load the NCAR Graphics library ngmath.

SEE ALSO

       csagrid, csa2xs, csa2ls, 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.