function cvt_dataset ( )

%*****************************************************************************80
%
%% CVT_DATASET generates a CVT dataset and writes it to a file.
%
%  Discussion:
%
%    This program is meant to be used interactively.  It's also
%    possible to prepare a simple input file beforehand and use it
%    in batch mode.
%
%    The program requests input values from the user:
%
%    * DIM_NUM, the spatial dimension,
%    * N, the number of points to generate,
%    * SEED, a seed to use for random number generation;
%    * INIT, initialize the points:
%      ** file, by reading data from file;
%      ** 'GRID', picking points from a grid;
%      ** 'HALTON', from a Halton sequence;
%      ** 'RAND', using MATLAB's RAND function;
%      ** 'UNIFORM', using a simple uniform RNG;
%      ** 'USER', refers to the "USER" routine;
%    * IT_MAX, the maximum number of iterations;
%    * IT_FIXED, the number of iterative steps to take
%      using a fixed set of sampling points.
%    * SAMPLE, how to conduct the sampling:
%      ** 'GRID', picking points from a grid;
%      ** 'HALTON', from a Halton sequence;
%      ** 'RAND', using MATLAB's RAND function;
%      ** 'UNIFORM', using a simple uniform RNG;
%      ** 'USER', refers to the "USER" routine;
%    * SAMPLE_NUM, the number of sampling points;
%    * BATCH, the number of sampling points to create at one time;
%    * OUTPUT, a file into which the data can be stored.
%
%    To indicate that no further computations are desired, it is 
%    enough to input a nonsensical value, such as -1.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    04 July 2005
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Qiang Du, Vance Faber, and Max Gunzburger,
%    Centroidal Voronoi Tessellations: Applications and Algorithms,
%    SIAM Review,
%    Volume 41, 1999, pages 637-676.
%
  DEBUG = 1;

  timestamp ( );

  fprintf ( 1, '\n' );
  fprintf ( 1, 'CVT_DATASET\n' );
  fprintf ( 1, '  MATLAB version\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Generate a CVT dataset.\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  This program is meant to be used interactively.\n' );
  fprintf ( 1, '  It is also possible to prepare a simple input \n' );
  fprintf ( 1, '  file beforehand and use it in batch mode.\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  The program requests input values from the user:\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  * DIM_NUM, the spatial dimension,\n' );
  fprintf ( 1, '  * N, the number of points to generate,\n' );
  fprintf ( 1, '  * SEED, a seed to use for random number generation,\n' );
  fprintf ( 1, '  * INIT, initialize the points:\n' );
  fprintf ( 1, '    ** file, read data from a file;\n' );
  fprintf ( 1, '    ** ''GRID'', by picking points from a grid;\n' );
  fprintf ( 1, '    ** ''HALTON'', from a Halton sequence;\n' );
  fprintf ( 1, '    ** ''RAND'', using MATLAB''s RAND function;\n' );
  fprintf ( 1, '    ** ''UNIFORM'', using a simple uniform RNG;\n' );
  fprintf ( 1, '    ** ''USER'', refers to the USER routine;\n' );
  fprintf ( 1, '  * IT_MAX, the maximum number of iterations.\n' );
  fprintf ( 1, '  * IT_FIXED, the number of iterative steps to take\n' );
  fprintf ( 1, '    using a fixed set of sampling points.\n' );
  fprintf ( 1, '  * SAMPLE, how to conduct the sampling.\n' );
  fprintf ( 1, '    ** ''GRID'', by picking points from a grid;\n' );
  fprintf ( 1, '    ** ''HALTON'', from a Halton sequence;\n' );
  fprintf ( 1, '    ** ''RAND'', using MATLAB''s RAND function;\n' );
  fprintf ( 1, '    ** ''UNIFORM'', using a simple uniform RNG;\n' );
  fprintf ( 1, '    ** ''USER'', refers to the USER routine;\n' );
  fprintf ( 1, '  * SAMPLE_NUM, the number of sample points;\n' );
  fprintf ( 1, '  * BATCH, the number of sample points to create at a time;\n' );
  fprintf ( 1, '  * OUTPUT, a file into which the data is stored.\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  To indicate that no further computations are \n' );
  fprintf ( 1, '  desired, it is enough to input a nonsensical value, \n' );
  fprintf ( 1, '  such as -1.\n' );

  while ( 1 )

    fprintf ( 1, '  *\n' );
    fprintf ( 1, ' *\n' );
    fprintf ( 1, '*  Ready to generate a new dataset:\n' );
    fprintf ( 1, ' *\n' );
    fprintf ( 1, '  *\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  DIM_NUM is the spatial dimension.\n' );
    fprintf ( 1, '  (Try ''2'' if you have no preference.)\n' );
    fprintf ( 1, '  (Any value less than 1 terminates execution.)\n' );
    dim_num = [];
    dim_num = input ( '  Enter DIM_NUM:  ' );

    fprintf ( 1, '  User input DIM_NUM = %12d\n', dim_num );

    if ( dim_num < 1 )
      fprintf ( 1, '\n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of DIM_NUM = %12d\n', dim_num );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    fprintf ( 1, '\n' );
    fprintf ( 1, '  N is the number of points to generate.\n' );
    fprintf ( 1, '  (Try ''25'' if you have no preference.)\n' );
    fprintf ( 1, '  (Any value less than 1 terminates execution.)\n' );
    n = [];
    n = input ( '  Enter N:  ' );

    fprintf ( 1, '  User input N = %12d\n', n );

    if ( n < 1 )
      fprintf ( 1, '\n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of N = %12d\n', n );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    fprintf ( 1, '\n' );
    fprintf ( 1, '  SEED is a seed for the random number generation.\n' );
    fprintf ( 1, '  (Try ''123456789'' if you have no preference.)\n' );
    fprintf ( 1, '  (Any value less than 0 terminates execution.)\n' );
    seed = [];
    seed = input ( '  Enter SEED:  ' );

    fprintf ( 1, '  User input SEED = %d\n', seed );

    if ( seed < 0 )
      fprintf ( 1, '\n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of SEED = %12d\n', seed );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    fprintf ( 1, '\n' );
    fprintf ( 1, '  INIT is the method of initializing the data:\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  file       read data from a file;\n' );
    fprintf ( 1, '  ''GRID''     by picking points from a grid;\n' );
    fprintf ( 1, '  ''HALTON''   from a Halton sequence;\n' );
    fprintf ( 1, '  ''RAND''     using MATLAB''s RAND function;\n' );
    fprintf ( 1, '  ''UNIFORM''  using a simple uniform RNG;\n' );
    fprintf ( 1, '  ''USER''     refers to the USER routine;\n' );
    fprintf ( 1, ' \n' );
    fprintf ( 1, '  (Try ''RAND'' if you have no preference.)\n' );
    fprintf ( 1, '  (A blank value terminates execution).\n' );
    fprintf ( 1, '  (Be sure to INCLUDE QUOTES around the string!\n' );
    fprintf ( 1, ' \n' );

    init_string = [];
    init_string = input ( '  Enter INIT:  ' );

    fprintf ( 1, '  User input INIT = "%s".\n', init_string );

    if ( s_len_trim ( init_string ) <= 0 )
      fprintf ( 1, '\n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of INIT \n' );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    if ( s_eqi ( init_string, 'RAND'  ) )
      init = -1;
    elseif ( s_eqi ( init_string, 'RANDOM' ) )
      init_string = 'RAND';
      init = -1;
    elseif ( s_eqi ( init_string, 'UNIFORM' ) )
      init = 0;
    elseif ( s_eqi ( init_string, 'HALTON'  ) )
      init = 1;
    elseif ( s_eqi ( init_string, 'GRID'    ) )
      init = 2;
    elseif ( s_eqi ( init_string, 'USER'    ) )
      init = 3;
    elseif ( 0 < s_len_trim ( init_string ) )
      init = 4;
    else
      fprintf ( 1, '\n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of INIT \n' );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    fprintf ( 1, '\n' );
    fprintf ( 1, '  IT_MAX is the maximum number of iterations.\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  An iteration carries out the following steps:\n' );
    fprintf ( 1, '  * the Voronoi region associated with each\n' );
    fprintf ( 1, '    generator is estimated by sampling;\n' );
    fprintf ( 1, '  * the centroid of each Voronoi region is estimated.\n' );
    fprintf ( 1, '  * the generator is replaced by the centroid.\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  If "enough" sampling points are used,\n' );
    fprintf ( 1, '  and "enough" iterations are taken, this process\n' );
    fprintf ( 1, '  will converge.\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  (Try ''50'' if you have no preference.)\n' );
    fprintf ( 1, '  (A negative value terminates execution).\n' );
    fprintf ( 1, '\n' );
    it_max = [];
    it_max = input ( '  Enter IT_MAX:  ' );

    fprintf ( 1, '  User input IT_MAX = %12d\n', it_max );

    if ( it_max < 0 )
      fprintf ( 1, ' \n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of IT_MAX = %12d\n', it_max );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    fprintf ( 1, '\n' );
    fprintf ( 1, '  IT_FIXED is the number of consecutive iterations\n' );
    fprintf ( 1, '  to take with a fixed set of sample points.\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  Setting IT_FIXED to 1 means a new set of sample\n' );
    fprintf ( 1, '  points is generated on every iterative step;\n' );
    fprintf ( 1, '  Setting IT_FIXED equal to IT_MAX means a single set\n' );
    fprintf ( 1, '  of sample points is used for the entire iteration.\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  Any value between 1 and IT_MAX is reasonable.\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  (Try "%d" if you do not have a preference).\n', it_max );
    fprintf ( 1, '  (A 0 or negative value terminates execution).\n' );
    fprintf ( 1, '\n' );
    it_fixed = [];
    it_fixed = input ( '  Enter IT_FIXED:  ' );

    fprintf ( 1, '  User input IT_FIXED = %12d\n', it_fixed );

    if ( it_max < 0 )
      fprintf ( 1, ' \n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of IT_FIXED = %12d\n', it_fixed );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    fprintf ( 1, '\n' );
    fprintf ( 1, '  SAMPLE is the method of sampling the region:\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  ''GRID''     by picking points from a grid;\n' );
    fprintf ( 1, '  ''HALTON''   from a Halton sequence;\n' );
    fprintf ( 1, '  ''RAND''     using MATLAB''s RAND function;\n' );
    fprintf ( 1, '  ''UNIFORM''  using a simple uniform RNG;\n' );
    fprintf ( 1, '  ''USER''     refers to the USER routine;\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  (Try ''RAND'' if you have no preference.)\n' );
    fprintf ( 1, '  (A blank value terminates execution).\n' );
    fprintf ( 1, '  (Be sure to INCLUDE QUOTES around the string!\n' );
    fprintf ( 1, '\n' );

    sample_string = [];
    sample_string = input ( '  Enter SAMPLE:  ' );

    fprintf ( 1, '  User input SAMPLE = "%s".\n', sample_string );

    if ( s_len_trim ( sample_string ) <= 0 )
      fprintf ( 1, '\n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of SAMPLE \n' );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    if ( s_eqi ( sample_string, 'RAND'  ) )
      sample = -1;
    elseif ( s_eqi ( sample_string, 'RANDOM' ) )
      sample = -1;
      sample_string = 'RAND';
    elseif ( s_eqi ( sample_string, 'UNIFORM' ) )
      sample = 0;
    elseif ( s_eqi ( sample_string, 'HALTON'  ) )
      sample = 1;
    elseif ( s_eqi ( sample_string, 'GRID'    ) )
      sample = 2; 
    elseif ( s_eqi ( sample_string, 'USER'    ) )
      sample = 3; 
    else
      fprintf ( 1, '\n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of SAMPLE \n' );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    fprintf ( 1, '\n' );
    fprintf ( 1, '  SAMPLE_NUM is the number of sample points.\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  The Voronoi regions will be explored by generating\n' );
    fprintf ( 1, '  SAMPLE_NUM points.  For each sample point, the\n' );
    fprintf ( 1, '  nearest generator is found.  Using more points\n' );
    fprintf ( 1, '  gives a better estimate of these regions.\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  SAMPLE_NUM should be much larger than N, the\n' );
    fprintf ( 1, '  number of generators.\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  (Try ''10000'' if you have no preference.)\n' );
    fprintf ( 1, '  (A zero or negative value terminates execution.)\n' );
    fprintf ( 1, '\n' );

    sample_num = [];
    sample_num = input ( '  Enter SAMPLE_NUM:  ' );

    fprintf ( 1, '  User input SAMPLE_NUM = %12d\n', sample_num );

    if ( sample_num <= 0 )
      fprintf ( 1, '\n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of SAMPLE_NUM = %12d\n', sample_num );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    fprintf ( 1, '\n' );
    fprintf ( 1, '  BATCH is the number of sample points to create\n' );
    fprintf ( 1, '  at one time\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  BATCH should be between 1 and SAMPLE_NUM.\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  It is FASTER to set BATCH to SAMPLE_NUM;\n' );
    fprintf ( 1, '  setting BATCH to 1 requires the least memory.\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  (Try ''%d'' if you have no preference.)\n', ...
      min ( 1000, sample_num ) );
    fprintf ( 1, '  (A zero or negative value terminates execution.)\n' );
    fprintf ( 1, '\n' );

    batch = [];
    batch = input ( '  Enter BATCH:  ' );

    fprintf ( 1, '  User input BATCH = %12d\n', batch );

    if ( batch <= 0 )
      fprintf ( 1, '\n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of BATCH = %12d\n', batch );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    fprintf ( 1, '\n' );
    fprintf ( 1, '  OUTPUT is a file into which the data is stored;\n' );
    fprintf ( 1, '\n' );
    fprintf ( 1, '  (Try ''cvt.txt'' if you have no preference.)\n' );
    fprintf ( 1, '  (A blank value terminates execution).\n' );
    fprintf ( 1, '  (Be sure to INCLUDE QUOTES around the string!\n' );
    fprintf ( 1, ' \n' );

    file_out_name = [];
    file_out_name = input ( '  Enter OUTPUT:  ' );

    fprintf ( 1, '  User input OUTPUT = "%s".\n', file_out_name );

    if ( s_len_trim ( file_out_name ) <= 0 )
      fprintf ( 1, '\n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of OUTPUT \n' );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end

    if ( s_len_trim ( file_out_name ) <= 0 )
      fprintf ( 1, '\n' );
      fprintf ( 1, 'CVT_DATASET\n' );
      fprintf ( 1, '  The input value of OUTPUT \n' );
      fprintf ( 1, '  is interpreted as a request for termination.\n' );
      fprintf ( 1, '  Normal end of execution.\n' );
      break
    end
%
%  Initialize the data.
%
    if ( init == 4 )
      r = data_read ( sample_string, dim_num, n );
    else
      r = [];
    end

    seed_init = seed;
    
    [ r, seed, it_num, it_diff, energy ] = cvt ( dim_num, n, batch, init, ...
      sample, sample_num, it_max, it_fixed, seed, r );
%
%  Write the data to a file.
%
    comment = 0;

    cvt_write ( dim_num, n, batch, seed_init, seed, init_string, it_max, ...
      it_fixed, it_num, it_diff, energy, sample_string, sample_num, ...
      r, file_out_name, comment );

    fprintf ( 1, '\n' );
    fprintf ( 1, '  The data was written to the file "%s".\n', ...
      file_out_name );

  end

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Final value of SEED = %d\n', seed );
  fprintf ( 1, '\n' );
  timestamp ( );

  return
end