new_contents: 
  
  import numpy as np
  import matplotlib.pyplot as plt
  import os
  #figdir = os.path.join(os.environ["PYPROBML"], "figures")
  figdir = "../figures";
  def save_fig(fname): plt.savefig(os.path.join(figdir, fname))
  
  
  from scipy.stats import nbinom
  
  
  
  xs = np.arange(50);
  fig, ax = plt.subplots(1,1)
  p = 0.5; r = 1;
  probabilities = nbinom.pmf(xs, r, p)
  ax.bar(xs, probabilities)
  ax.set_title('NB(r={:.2f}, p={:.2f})'.format(r, p))
  save_fig('negbinomPlot_r{}_p{}.png'.format(int(r*10), int(p*10)))
  plt.show()
  
  fig, ax = plt.subplots(1,1)
  p = 0.5; r = 10;
  probabilities = nbinom.pmf(xs, r, p)
  ax.bar(xs, probabilities)
  ax.set_title('NB(r={:.2f}, p={:.2f})'.format(r, p))
  save_fig('negbinomPlot_r{}_p{}.png'.format(int(r*10), int(p*10)))
  plt.show()
  
  
  
subject: make plot of negative binomial