#! /usr/bin/env python3
#
def corkscrew_plot3d ( ):

#*****************************************************************************80
#
## corkscrew_plot3d() plots a 3D corkscrew function.
#
#  Licensing:
#
#    This code is distributed under the MIT license.
#
#  Modified:
#
#    27 September 2026
#
#  Author:
#
#    John Burkardt
#
  import matplotlib
  import numpy as np
  import platform

  print ( '' )
  print ( 'corkscrew_plot3d():' )
  print ( '  matplotlib version: ' + matplotlib.__version__ )
  print ( '  numpy version:      ' + np.version.version )
  print ( '  python version:     ' + platform.python_version ( ) )
  print ( '  Define (X,Y,Z) data on a 3D curve.' )

  header = 'corkscrew'
#
#  Define the data.
#
  n = 101
  z = np.linspace ( -2.0, 2.0, n )
  theta_min = - 6.0 * np.pi
  theta_max = + 6.0 * np.pi
  theta = np.linspace ( theta_min, theta_max, n )
  r = 1.0 + z**2
  x = r * np.sin ( theta )
  y = r * np.cos ( theta )
#
#  Create the data file.
#
  data_filename = header + '_data.txt'
  data_unit = open ( data_filename, 'wt' )
  for i in range ( 0, n ):
    s = ( '  %14.6g  %14.6g  %14.6g\n' % ( x[i], y[i], z[i] ) )
    data_unit.write ( s )
  data_unit.close ( )
  print ( '  Created data file "' + 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 "X"\n' )
  command_unit.write ( 'set ylabel "Y"\n' )
  command_unit.write ( 'set zlabel "Z"\n' )
  command_unit.write ( 'set title "Corkscrew curve"\n' )
  command_unit.write ( 'set grid\n' )
  command_unit.write ( 'set timestamp\n' )
  command_unit.write ( 'set style data lines\n' )
  command_unit.write ( 'splot "' + data_filename + \
    '" using 1:2:3 with lines\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 ( )
  corkscrew_plot3d ( )
  timestamp ( )