text: import os.path
  import sys
  import numpy as np
  
  try:
      import matplotlib.pyplot as plt
  except:
      print("Error importing pyplot from matplotlib, please install matplotlib package first...")
      sys.tracebacklimit=0
      raise Exception("Importing matplotlib failed")
  
  if __name__ == '__main__':
  
      #b = np.loadtxt('/home/liuq0a/tests/marmousi_onshore_SRVM_new10_1/output.stats/misfit')
      b = np.loadtxt('Eigen_values.txt')
      b0 = b[0]
      #b = b / b[0]
  
      print "b = ", b[:]
  
      nb = np.size(b)
  
      plt.figure(figsize=(10,5))
      ax = plt.subplot(111)
      plt.plot(range(1,nb+1),b,'o-',color="black",linewidth=2)
      #plt.plot(range(na),a,label='$L-BFGS$',color="blue",linewidth=2)
      ax.legend()
      ax.set_yscale('log')
      plt.xlabel("ORDER")
      plt.ylabel("EIGENVALUE")
      plt.xlim(0,70)
      #plt.ylim(5.0e-3,1.1)
      #plt.title("MARMOUSI")
      plt.savefig("fig3.png")
  
  