#! /usr/bin/env python
#
def t_polynomial_plot ( n_num, n_val, filename ):

#*****************************************************************************80
#
## T_POLYNOMIAL_PLOT plots Chebyshev polynomials T(n,x).
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    21 July 2015
#
#  Author:
#
#    John Burkardt
#
#  Parameters:
#
#    Input, integer N_NUM, the number of polynomials to plot.
#
#    Input, integer N_VAL(N_NUM), the degree of each polynomial.
#
#    Input, string FILENAME, the name into which the graphics information is
#    to be stored.  Note that the PNG format will be used.
#
  import matplotlib.pyplot as plt
  import numpy as np
  from t_polynomial import t_polynomial

  a = -1.0
  b = +1.0
  m = 501
  x = np.linspace ( a, b, m )

  for i in range ( 0, n_num ):
    n = n_val[i]
    y = t_polynomial ( m, n, x )
    plt.plot ( x, y, 'b-', linewidth = 2.0 )

  t = 'T(n,x), for n = '
  for i in range ( 0, n_num ):
    n = n_val[i]
    t = t + str ( n )
    if ( 1 < n_num and i < n_num - 1 ):
      t = t + ', '

  plt.title ( t )
  plt.grid ( True )
  plt.xlabel ( '<---X--->' )
  plt.ylabel ( '<---T(n,x)--->' )
  plt.savefig ( filename )
  plt.clf ( )

  print ( '  Created plot file "%s".' % ( filename ) )

  return

def t_polynomial_plot_test ( ):

#*****************************************************************************80
#
## T_POLYNOMIAL_PLOT_TEST tests T_POLYNOMIAL_PLOT.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    21 July 2015
#
#  Author:
#
#    John Burkardt
#
  import numpy as np
  import platform

  print ( '' )
  print ( 'T_POLYNOMIAL_PLOT_TEST:' )
  print ( '  Python version: %s' % ( platform.python_version ( ) ) )
  print ( '  Plot several Chebyshev T polynomials.' )

  n_num = 6
  n_val = np.array ( [ 0, 1, 2, 3, 4, 5 ] )
  filename = 't_polynomial_plot.png'

  t_polynomial_plot ( n_num, n_val, filename )
#
#  Terminate.
#
  print ( '' )
  print ( 'T_POLYNOMIAL_PLOT_TEST:' )
  print ( '  Normal end of execution.' )
  return

if ( __name__ == '__main__' ):
  from timestamp import timestamp
  timestamp ( )
  t_polynomial_plot_test ( )
  timestamp ( )