function pressure3_write ( file_name, node_num, node_p_variable, ...
  variable_num, node_c )

%% PRESSURE3_WRITE writes the pressures to a file.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    22 June 2005
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, string FILE_NAME, the file name.
%
%    Input, integer NODE_NUM, the number of nodes.
%
%    Input, integer NODE_P_VARIABLE(NODE_NUM),
%    is the index of the pressure variable associated with the node,
%    or -1 if there is no associated pressure variable.
%
%    Input, integer VARIABLE_NUM, the number of variables.
%
%    Input, real NODE_C(VARIABLE_NUM), the finite element coefficients.
%
  file_unit = fopen ( file_name, 'wt');

  if ( file_unit < 0 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'PRESSURE3_WRITE - Warning!\n' );
    fprintf ( 1, '  Could not write the file "%s".\n', file_name );
    return;
  end

  for node = 1 : node_num

    variable = node_p_variable(node);

    if ( 0 < variable )
      fprintf ( file_unit, '  %14f\n', node_c(variable) );
    end

  end

  fclose ( file_unit );

  return
end