# include <cmath>
# include <cstdlib>
# include <cstring>
# include <ctime>
# include <fstream>
# include <iomanip>
# include <iostream>

using namespace std;

int main ( );
void timestamp ( );

//****************************************************************************80

int main ( )

//****************************************************************************80
//
//  Purpose:
//
//    brownian_2d_plot() creates a line plot of two-dimensional Brownian motion.
//
//  Licensing:
//
//    This code is distributed under the MIT license.
//
//  Modified:
//
//    17 September 2026
//
//  Author:
//
//    John Burkardt
//
{
  string command_filename;
  string data_filename;
  string graphic_filename;
  string header = "brownian_2d";
  ofstream command_unit;

  timestamp ( );
  cout << "\n";
  cout << "brownian_2d_plot():\n";
  cout << "  C++ version\n";
  cout << "  Create a line plot two-dimensional Brownian motion.\n";
//
//  Set filenames.
//
  command_filename = header + "_commands.txt";
  graphic_filename = header + "_plot.png";
  data_filename = header + "_data.txt";
//
//  Create the command file.
//
  command_unit.open ( command_filename.c_str ( ) );

  command_unit << "# " << command_filename << "\n";
  command_unit << "#\n";
  command_unit << "# Usage:\n";
  command_unit << "#  gnuplot < " << command_filename << "\n";
  command_unit << "#\n";
  command_unit << "set term png\n";
  command_unit << "set output '" << graphic_filename << "'\n";
  command_unit << "set xlabel '<--- X --->'\n";
  command_unit << "set ylabel '<--- Y --->'\n";
  command_unit << "set title '1000 steps of Brownian Motion'\n";
  command_unit << "set grid\n";
  command_unit << "set timestamp\n";
  command_unit << "set style data lines\n";
  command_unit << "plot '" << data_filename << "' using 1:2 with lines lw 3\n" ;
  command_unit << "quit\n";

  command_unit.close ( );

  cout << "\n";
  cout << "  Plot commands stored in '" << command_filename << "'\n";
//
//  Terminate.
//
  cout << "\n";
  cout << "brownian_2d_plot():\n";
  cout << "  Normal end of execution.\n";
  cout << "\n";
  timestamp ( );

  return 0;
}
//****************************************************************************80

void timestamp ( )

//****************************************************************************80
//
//  Purpose:
//
//    timestamp() prints the current YMDHMS date as a time stamp.
//
//  Example:
//
//    31 May 2001 09:45:54 AM
//
//  Licensing:
//
//    This code is distributed under the MIT license. 
//
//  Modified:
//
//    19 March 2018
//
//  Author:
//
//    John Burkardt
//
{
# define TIME_SIZE 40

  static char time_buffer[TIME_SIZE];
  const struct std::tm *tm_ptr;
  std::time_t now;

  now = std::time ( NULL );
  tm_ptr = std::localtime ( &now );

  std::strftime ( time_buffer, TIME_SIZE, "%d %B %Y %I:%M:%S %p", tm_ptr );

  std::cout << time_buffer << "\n";

  return;
# undef TIME_SIZE
}