#!/usr/bin/python3 

# script animated_Coin.py
''' example to produce random numbers (0/1) 
    as obtained by throwing a coin
    animated fraction of heads vs. number of throws
    
.. author:: Guenter Quast <g.quast@kit.edu>

'''

# pyhton2 - python3 compatibility
from __future__ import print_function, division, unicode_literals

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as anim
import sys

nthrow=499    # how often to throw

#create a figure
fig=plt.figure(figsize=(7.5,7.5))
ax=fig.add_subplot(1,1,1)
ax.grid(True)
ax.set_xlabel('N (number of trials)', size='x-large')
ax.set_ylabel('p ($N_{head} / N$)', size='x-large')
x=np.linspace(0.,nthrow,nthrow)
# plot expectation ...
ax.plot(x,0.5*np.ones(nthrow),'r--',lw=2)
# ... and error band
ax.plot(x,0.5+0.5/np.sqrt(x),'b--',lw=2)
ax.plot(x,0.5-0.5/np.sqrt(x),'b--',lw=2)
txt1 = ax.text(0.1, 0.9, ' ', transform=ax.transAxes,size='xx-large',
  bbox=dict(facecolor='silver', edgecolor='r', boxstyle='circle', pad=0.5))
txt2 = ax.text(0.81, 0.93, ' ', transform=ax.transAxes,size='x-large',
                    backgroundcolor='white')
#
# throw the coin and plot N_head over (number of trials) 
Nh=0
N=0
def animate(i):
  global N,Nh, r, x
  N+=1
  if np.random.rand()>0.5:
    Nh+=1
    t=' O '
  else:
    t='-1-'
  r=float(Nh)/float(N)
  # plot result 
  graph, = ax.plot(float(N), r, 'g.')
  txt1.set_text(t)
  txt2.set_text('N = %i' %(N))
  return graph, txt1,txt2
#
# show as animated (=updating) graph
print(('\n*==* script ' + sys.argv[0]+' executing'))
ani=anim.FuncAnimation(fig, animate, nthrow, interval=20, blit=False,
                         init_func=None, fargs=None, repeat=False)
plt.show()