text: from pylab import *
  import postgkyl as pg
  
  style.use('../postgkyl.mplstyle')
  
  komega = pg.GData("iso-4-buneman_frequencies.bp").getValues()
  k = komega[:,0]
  
  numk = k.shape[0]
  ntot = komega.shape[1]
  numEig = int((ntot-3)/2)
  
  omega_r = zeros((numk, numEig), float)
  omega_i = zeros((numk, numEig), float)
  for i in range(numk):
      omega_r[i,:] = komega[i,3::2]
      omega_i[i,:] = komega[i,4::2]
  
  omega_growing_r = zeros((numk, numEig), float)
  for i in range(numk):
      for n in range(numEig):
          if omega_i[i,n] < 1e-3:
              omega_r[i,n] = -1 # zap these so the are not seen
  
  figure(1)
  for i in range(numEig):
      plot(k, omega_r[:,i], '.', color='r', markersize=2)
  
  gca().set_ylim([0,2.5])
  grid()
  
  show()
  