#! /usr/bin/env python3
#
def brownian_2d_plot ( ):

#*****************************************************************************80
#
## brownian_2d_plot() plots Brownian motion.
#
#  Licensing:
#
#    This code is distributed under the MIT license.
#
#  Modified:
#
#    16 September 2026
#
#  Author:
#
#    John Burkardt
#
  import matplotlib
  import numpy as np
  import platform

  print ( '' )
  print ( 'brownian_2d_plot():' )
  print ( '  numpy version:      ' + np.version.version )
  print ( '  python version:     ' + platform.python_version ( ) )
  print ( '  Plot Brownian motion.' )
#
#  Set filenames.
#
  header = 'brownian_2d'
  command_filename = header + '_commands.txt'
  data_filename = header + '_data.txt'
  graphic_filename = header + '_plot.png'
#
#  Create commands.
#
  command_unit = open ( command_filename, 'wt' )

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

  command_unit.close ( )
  print ( '  Created command file "' + command_filename + '"' )

  return

def timestamp ( ):

#*****************************************************************************80
#
## timestamp() prints the date as a timestamp.
#
#  Licensing:
#
#    This code is distributed under the MIT license. 
#
#  Modified:
#
#    21 August 2019
#
#  Author:
#
#    John Burkardt
#
  import time

  t = time.time ( )
  print ( time.ctime ( t ) )

  return

if ( __name__ == '__main__' ):
  timestamp ( )
  brownian_2d_plot ( )
  timestamp ( )