function nodes_write ( node_num, node_xy, output_filename )

%% NODES_WRITE writes the nodes to a file.
%
%  Modified:
%
%    24 March 2005
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, integer NODE_NUM, the number of nodes.
%
%    Input, real NODE_XY(2,NODE_NUM), the X and Y coordinates of nodes.
%
%    Input, character OUTPUT_FILENAME(*), the name of the file
%    in which the data should be stored.
%
  output_unit = fopen ( output_filename, 'wt');

  if ( output_unit < 0 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'NODES_WRITE - Warning!\n' );
    fprintf ( 1, '  Could not write the nodes file.\n' );
    return;
  end

  for node = 1 : node_num

    x = node_xy(1,node);
    y = node_xy(2,node);

    fprintf ( output_unit, '%8f  %8f\n', x, y );

  end

  fclose ( output_unit );