NAME

       CSA3S - cubic spline approximation, simple entry for three-dimensional input

SYNOPSIS

       CALL CSA3S (NI, XI, UI, KNOTS, NXO, NYO, NZO, XO, YO, ZO,
                   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 - Z coordinates of the input data points.  XI  is
                   dimensioned  for  3  x  NI.   XI(1,L)  is  the X coordinate, XI(2,L) is the Y coordinate, and
                   XI(2,L) is the Z 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 XI(L) for L=1,NI.

       KNOTS       (integer, input) An array dimensioned for 3 containing the number of knots to be used in each
                   coordinate  direction for constructing the approximation spline.  KNOTS(I) must be at least 4
                   for I=1,3.  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 in the output grid.

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

       NZO         (integer, input) The number of Z 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.

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

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

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

       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 CSA3S.

ACCESS

       To use CSA3XS, load the NCAR Graphics library ngmath.

SEE ALSO

       csagrid, csa3xs, csa3ls, 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                                     CSA3S(3NCARG)