#!/usr/bin/env python
# script animate_wave.py
''' example of a simpe animation: running wave
.. author:: Guenter Quast <g.quast@kit.edu>
'''

# dependencies:  PYTHON v2.7, numpy, matplotlib
# last modified: 
#--------------------------------------------------------------

# pyhton2 - python3 compatibility
from __future__ import division
from __future__ import absolute_import
from __future__ import print_function
from __future__ import unicode_literals
# 
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as anim
import sys

##### ---- main Program starts here -----
if __name__ == "__main__":

  fig=plt.figure(figsize=(7.5,7.5))
  ax=fig.add_subplot(1,1,1)
  ax.grid(True)
  ax.set_title('sin(kx - $\\omega$t)', size='xx-large')
  ax.set_xlabel('normalized position $x/\\lambda$')
  ax.set_ylabel('normalized amplitude $A / A_0$')
  x=np.linspace(0.,2.,200)
  nperiods=2
  nrep=200
  k,omega=2*np.pi,2*np.pi

  timetxt = ax.text(0.25, 0.93, ' ', transform=ax.transAxes,size='x-large',
                    backgroundcolor='white')
  y=np.sin(k*x)
  graph, = ax.plot(x,y,'--', color='black')

  def animate(n):
    t=nperiods*float(n)/nrep
    y=np.sin(k*x - omega*t)
    graph, = ax.plot(x,y,'-', color='blue', lw=2)
    timestamp='t = %.2f $\\cdot$ T' %(t)
    timetxt.set_text(timestamp)
    return graph, timetxt

  print('\n*==* script ' + sys.argv[0]+' executing')
  ani=anim.FuncAnimation(fig, animate, nrep, interval=50, blit=True,
                         init_func=None, fargs=None, repeat=True)
  plt.show()