function velocity6_write ( file_name, node_num, node_u_variable, ...
  node_v_variable, variable_num, node_c ) 

%% VELOCITY6_WRITE writes the velocities to a file.
%
%  Modified:
%
%    06 September 2006
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, character FILE_NAME, the file name.
%
%    Input, integer NODE_NUM, the number of nodes.
%
%    Input, integer NODE_U_VARIABLE(NODE_NUM), NODE_V_VARIABLE(NODE_NUM),
%    the indices of the horizontal and vertical velocity variables
%    associated with the node, or -1 if there is none.
%
%    Input, integer VARIABLE_NUM, the number of variables.
%
%    Input, real NODE_C(NODE_NUM), the coefficients of the solution.
%
  output_unit = fopen ( file_name, 'wt' );

  if ( output_unit < 0 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'VELOCITY6_WRITE - Warning!\n' );
    fprintf ( 1, '  Could not write the velocity file.\n' );
    return
  end

  for node = 1 : node_num

    u_index = node_u_variable(node);

    if ( 0 < u_index )
      u = node_c(u_index);
    else
      u = 0.0;
    end

    v_index = node_v_variable(node);

    if ( 0 < v_index )
      v = node_c(v_index);
    else
      v = 0.0;
    end

    fprintf ( output_unit, '  %14f  %14f\n', u, v );

  end

  fclose ( output_unit );