function nodes3_write ( file_name, node_num, node_xy, node_type )

%% NODES3_WRITE writes the pressure nodes to a file.
%
%  Modified:
%
%    22 June 2005
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, integer NODE_NUM, the number of nodes.
%
%    Input, real NODE_XY(2,NODE_NUM), the coordinates of nodes.
%
%    Input, integer NODE_TYPE(NODE_NUM), determines if the node is a 
%    vertex or midside node.
%    1, the node is a vertex (P, U, V variables are associated with it).
%    2, the node is a midside node (only U and V variables are associated.)
%
  file_unit = fopen ( file_name, 'wt');

  if ( file_unit < 0 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'NODES3_WRITE - Warning!\n' );
    fprintf ( 1, '  Could not write the file "%s".\n', file_name );
    return;
  end

  for node = 1 : node_num

    if ( node_type(node) == 1 )
      fprintf ( file_unit, '%8f  %8f\n', node_xy(1:2,node) );
    end

  end

  fclose ( file_unit );