function grid_write ( m, n, seed, center, r, file_out_name )

%% GRID_WRITE writes a grid dataset to a file.
%
%  Discussion:
%
%    The initial lines of the file are comments, which begin with a
%    '#' character.
%
%    Thereafter, each line of the file contains the NDIM-dimensional
%    components of the next entry in the dataset.
%
%  Modified:
%
%    04 May 2005
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, integer M, the spatial dimension.
%
%    Input, integer N, the number of points.
%
%    Input, integer SEED, the seed for the random number generator.
%
%    Input, integer CENTER, specifies the 1D grid centering:
%    1: first point is 0.0, last point is 1.0;
%    2: first point is 1/(N+1), last point is N/(N+1);
%    3: first point is 0, last point is (N-1)/N;
%    4: first point is 1/N, last point is 1;
%    5: first point is 1/(2*N), last point is (2*N-1)/(2*N);
%
%    Input, real R(M,N), the points.
%
%    Input, string FILE_OUT_NAME, the name of the output file.
%
  file_out_unit = fopen ( file_out_name, 'w' );

  if ( file_out_unit < 0 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'GRID_WRITE - Fatal error!\n' );
    fprintf ( 1, '  Could not open the output file:\n' );
    fprintf ( 1, '  "%s".\n', file_out_name );
    error ( 'GRID_WRITE - Fatal error!' );
  end

  today = timestring;

  fprintf ( file_out_unit, '#  %s\n', file_out_name );
  fprintf ( file_out_unit, '#  created by GRID_WRITE.M\n' );
  fprintf ( file_out_unit, '#\n' );
  fprintf ( file_out_unit, '#  File generated on %s\n', timestring );
  fprintf ( file_out_unit, '#\n' );
  fprintf ( file_out_unit, '#  M =    %d\n', m );
  fprintf ( file_out_unit, '#  N =    %d\n', n );
  fprintf ( file_out_unit, '#  EPSILON (unit roundoff ) = %e\n', ...
    r8_epsilon ( 'DUMMY' ) );
  fprintf ( file_out_unit, '#  Initial SEED =   %d\n', seed );
  fprintf ( file_out_unit, '#  Grid centering = %d\n', center );
  fprintf ( file_out_unit, '#\n' );

  for j = 1 : n
    for i = 1 : m
      fprintf ( file_out_unit, '  %10f', r(i,j) );
    end
    fprintf ( file_out_unit, '\n' );
  end

  fclose ( file_out_unit );