#!/usr/bin/env python
# script py.py
''' calculate area of a circle with MC method,
with graphical illustration
.. 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 sys

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

  npoints=10000
  
  insidex=[]
  insidey=[]
  outsidex=[]
  outsidey=[]

  for i in range(npoints):
    rvec=np.random.rand(2)
    if (np.sum(rvec**2)<=1.):
      insidex.append(rvec[0]) 
      insidey.append(rvec[1]) 
    else:
      outsidex.append(rvec[0])  
      outsidey.append(rvec[1])  

  fig=plt.figure(figsize=(7.5,7.5))
  ax=fig.add_subplot(1,1,1)
  ax.scatter(insidex,insidey,s=1,color='green')
  ax.scatter(outsidex,outsidey,s=1,color='red')

  pi=4.*float(len(insidex))/float((len(insidex)+len(outsidex)))
  print('\n*==* script ' + sys.argv[0]+' executing')
  print('   Total number of random points %i' % (len(insidex)+len(outsidex)) )
  print('   Points inside circle %i' % len(insidex) )
  print('   ==> pi= %.3f' % pi)
  
  plt.show()