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

#*****************************************************************************80
#
## mark_points() shows how to add marked points to a plot.
#
#  Discussion:
#
#    You can't add more items to a gnuplot() plot once it's created, 
#    so if you want to plot some points, and then include some markers,
#    then you have to create some auxilliary data files identifying those
#    marked points, and refer to them in an extra-long single plot() command.
#   
#  Licensing:
#
#    This code is distributed under the MIT license.
#
#  Modified:
#
#    04 December 2025
#
#  Author:
#
#    John Burkardt
#
  import matplotlib
  import numpy as np
  import platform

  print ( '' )
  print ( 'mark_points():' )
  print ( '  matplotlib version: ' + matplotlib.__version__ )
  print ( '  numpy version:      ' + np.version.version )
  print ( '  python version:     ' + platform.python_version ( ) )
  print ( '  mark_points() plots a damped sine function over a range.' )
  print ( '  Mark the first data point green, and the last one red..' )
#
#  Define the damped_sine data.
#
  rho0 = 1.0
  n = 101
  rho = np.linspace ( -12.0, +12.0, n )
  c = np.ones ( n )
  i = np.where ( rho != 0.0 )
  c[i] = rho0 * np.sin ( np.abs ( rho[i] ) / rho0 ) / np.abs ( rho[i] )
#
#  Request a plot
#
  mark_points_plot ( n, rho, c, 'mark_points', 'Marking points in gnuplot' )

  return

def mark_points_plot ( n, rho, c, header, title ):

#*****************************************************************************80
#
## mark_points_plot() adds two marked points to a plot.
#
#  Licensing:
#
#    This code is distributed under the MIT license.
#
#  Modified:
#
#    02 September 2026
#
#  Author:
#
#    John Burkardt
#
#  Input:
#
#    integer N, the number of arguments.
#
#    real RHO(N), the arguments.
#
#    real C(N), the correlations.
#
#    string HEADER, an identifier for the files.
#
#    string TITLE, a title for the plot.
#

#
#  Create the main data file.
#
  data_filename = header + '_data.txt'
  data_unit = open ( data_filename, 'wt' )
  for i in range ( 0, n ):
    s = ( '  %14.6g  %14.6g\n' % ( rho[i], c[i] ) )
    data_unit.write ( s )
  data_unit.close ( )
  print ( '  Created data file "' + data_filename + '"' )
#
#  Create a data file for the green point.
#
  start_data_filename = header + '_start_data.txt'
  data_unit = open ( start_data_filename, 'wt' )
  s = ( '  %14.6g  %14.6g\n' % ( rho[0], c[0] ) )
  data_unit.write ( s )
  data_unit.close ( )
  print ( '  Created data file "' + start_data_filename + '"' )
#
#  Create a data file for the red point.
#
  end_data_filename = header + '_end_data.txt'
  data_unit = open ( end_data_filename, 'wt' )
  s = ( '  %14.6g  %14.6g\n' % ( rho[n-1], c[n-1] ) )
  data_unit.write ( s )
  data_unit.close ( )
  print ( '  Created data file "' + end_data_filename + '"' )
#
#  Create the command file.
#
  command_filename = header + '_commands.txt'
  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 "' + header + '.png"\n' )
  command_unit.write ( 'set xlabel "Distance Rho"\n' )
  command_unit.write ( 'set ylabel "Correlation C(Rho)"\n' )
  command_unit.write ( 'set title "' + title + '"\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 lw 3 linecolor rgb "blue", \\\n' )
  command_unit.write ( '     "' + start_data_filename + \
    '" using 1:2 with points pointtype 7 pointsize 3 linecolor rgb "green", \\\n' )
  command_unit.write ( '     "' + end_data_filename + \
    '" using 1:2 with points pointtype 7 pointsize 3 linecolor rgb "red"\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 ( )
  mark_points ( )
  timestamp ( )