new_contents: import numpy as np
  import matplotlib.pyplot as plt
  import sys
  
  if sys.argc < 2:
      print "Usage ./plot_velocity_based_position_controller.py [File_name]"
      sys.exit(-1)
  
  data = np.genfromtxt(sys.argv[-1], delimiter=',')
  # 0 for x, 1 for y  2 for z and 3 for yaw
  plot_axis = 3;
  ts = (data[:,0] - data[0, 0])/1e9
  plt.figure(1+plot_axis)
  plt.subplot(2,1,1)
  plt.plot(ts, data[:, 1+plot_axis]);
  plt.ylabel('Error')
  plt.subplot(2,1,2)
  plt.plot(ts, data[:, 5+plot_axis]);
  plt.ylabel('Cumulative Error')
  plt.xlabel('Time (seconds)')
  plt.show()
  plt.figure(2+plot_axis)
  plt.plot(ts, data[:, 9+plot_axis])
  plt.ylabel('Control')
  plt.xlabel('Time (seconds)')
  
subject: Add plotting script for analyzing velocity based position controller