#!/usr/bin/env python
# script animate_pi.py
''' animated graphical illustration of determination of pi with MC method
.. author:: Guenter Quast <g.quast@kit.edu>
'''

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

# 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

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

  fig=plt.figure(figsize=(7.5,7.5))
  ax=fig.add_subplot(1,1,1)

  nin=0.
  nout=0.

  nrep=200
  npoints=50
  def animate(n):
    global nin,nout
    ix,iy,ox,oy=[],[],[],[]
    for j in range(npoints):
      r=np.random.rand(2)
      if (np.sum(r**2)<=1.):
        nin+=1.
        ix.append(r[0]) 
        iy.append(r[1]) 
      else:
        nout+=1.
        ox.append(r[0])  
        oy.append(r[1])  
    si=ax.scatter(ix,iy,s=1,color='green')
    so=ax.scatter(ox,oy,s=1,color='red')
    nt=nin+nout
    pi=4.*nin/(nt)
    tx=ax.text(0.25, 0.05, '%i points, $\\pi=$ %.3f' %(nt,pi),
      transform=ax.transAxes, backgroundcolor='white', size='x-large')
    return si,so,tx

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

  pi=4.*nin/(nin+nout)
  print(('   Total number of random points %i' % (nin+nout) ))
  print(('   Points inside circle %i' % nin ))
  print(('   ==> pi= %.3f' % pi))