function triangulation_quality ( input_node_filename, ...
  input_triangulation_filename )

%% MAIN is the main program for TRIANGULATION_QUALITY.
%
%  Discussion:
%
%    TRIANGULATION_QUALITY determines quality measures for a triangulation.
%
%    The code has been modified to 'allow' 6-node triangulations.
%    However, no effort is made to actually process the midside nodes.
%    Only information from the vertices is used.
%
%    The three quality measures are:
%
%      ALPHA_MEASURE
%      AREA_MEASURE
%      Q_MEASURE
%
%    In each case, the ideal value of the quality measure is 1, and
%    the worst possible value is 0.
%
%    The program also prints out the geometric bandwidth, which is the
%    bandwidth of the adjacency matrix of the nodes.
%
%  Modified:
%
%    30 December 2006
%
%  Author:
%
%    John Burkardt
%
%  Local parameters:
%
%    Local, integer DIM_NUM, the spatial dimension.
%
%    Local, integer NODE_NUM, the number of nodes.
%
%    Local, real NODE_XY(DIM_NUM,NODE_NUM), the point set.
%
%    Local, integer TRIANGLE_NODE(TRIANGLE_ORDER,TRIANGLE_NUM), 
%    lists the nodes that make up each triangle.
%
%    Local, integer TRIANGLE_NUM, the number of triangles.
%
%    Local, integer TRIANGLE_ORDER, the order of the triangles, 
%    either 3 or 6.
%
  fprintf ( 1, '\n' );
  timestamp;

  fprintf ( 1, '\n' );
  fprintf ( 1, 'TRIANGULATION_QUALITY:\n' );
  fprintf ( 1, '  (MATLAB version):\n' );
  fprintf ( 1, '  Compute triangulation quality measures.\n' );
%
%  If at least one command line argument, it's the node file name.
%
  if ( nargin < 1 )

    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRIANGULATION_QUALITY:\n' );

    input_node_filename = input ( ...
      'Please enter the name of the node coordinate file ' );

  end
%
%  If at least two arguments, the second is the triangulation file.
%
  if ( nargin < 2 )

    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRIANGULATION_QUALITY:\n' );
    input_triangulation_filename = input ( ...
      '  Please enter the name of the triangulation file.' );

  end
%
%  Read the node data.
%
  [ dim_num, node_num ] = dtable_header_read (  input_node_filename );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the header of "%s".', input_node_filename );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Spatial dimension DIM_NUM = %d\n', dim_num );
  fprintf ( 1, '  Number of points NODE_NUM = %d\n', node_num );

  if ( dim_num ~= 2 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRIANGULATION_QUALITY - Fatal error!\n' );
    fprintf ( 1, '  Dataset must have spatial dimension 2.\n' );
    error ( 'TRIANGULATION_QUALITY - Fatal error!' );
  end

  node_xy = dtable_data_read ( input_node_filename, dim_num, node_num );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the data in "%s".\n', input_node_filename );

  r8mat_transpose_print_some ( dim_num, node_num, node_xy, 1, 1, 5, 5, ...
    '  5 by 5 portion of data read from file:' );
%
%  Read the triangulation data.
%
  [ triangle_order, triangle_num ] = itable_header_read ( ...
    input_triangulation_filename );

  if ( triangle_order ~= 3 & triangle_order ~= 6 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRIANGULATION_QUALITY - Fatal error!\n' );
    fprintf ( 1, '  Data is not for a 3-node or 6-node triangulation.\n' );
    error ( 'TRIANGULATION_QUALITY - Fatal error!' );
  end

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the header of "%s".\n', ...
    input_triangulation_filename );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Triangle order = %d\n', triangle_order );
  fprintf ( 1, '  Number of triangles TRIANGLE_NUM  = %d\n', ...
    triangle_num );

  triangle_node = itable_data_read ( input_triangulation_filename, ...
    triangle_order, triangle_num );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the data in "%s".\n', ...
    input_triangulation_filename );

  i4mat_transpose_print_some ( triangle_order, triangle_num, ...
    triangle_node, 1, 1, triangle_order, 10, ...
    '  Portion of TRIANGLE_NODE:' );

  value = alpha_measure ( node_num, node_xy, triangle_order, ...
    triangle_num, triangle_node );
  fprintf ( 1, '  The minimum angle measure    Alpha = %f\n', value );

  value = area_measure ( node_num, node_xy, triangle_order, ...
    triangle_num, triangle_node );
  fprintf ( 1, '  The area ratio measure     A-Ratio = %f\n', value );

  value = q_measure ( node_num, node_xy, triangle_order, triangle_num, ...
    triangle_node );
  fprintf ( 1, '  The triangle uniformity measure  Q = %f\n', value );

  [ ml, mu, m ] = bandwidth_mesh ( triangle_order, triangle_num, ...
    triangle_node );

  fprintf ( 1, '  The geometric bandwidth          M = %d\n', m );

  fprintf ( 1, '\n' );
  fprintf ( 1, 'TRIANGULATION_QUALITY:\n' );
  fprintf ( 1, '  Normal end of execution.\n' );

  fprintf ( 1, '\n' );
  timestamp;