title: Multiple y axis using matplotlib not working
body: <p>I have used following code to plot graph using matplotlib with 4 parameter <code>X=depth, y1=temp, y2=salinity, y3=velocity</code> but value of velocity is not display properly and 2nd and 3rd axes are not adjustable(scale value) as 1st when zoom that has constant scale value, how could i make it adjustable(scale value) ,I mean scale value will be variable for all axes when zoom in zoomout.</p>
  
  <pre><code> from mpl_toolkits.axes_grid1 import host_subplot
   import mpl_toolkits.axisartist as AA
   import matplotlib.pyplot as plt
   import numpy as np
  
   if 1:
  
      host = host_subplot(111, axes_class=AA.Axes)
      plt.subplots_adjust(right=0.75)
  
      par1 = host.twinx()
      par2 = host.twinx()
  
      offset = 60
      new_fixed_axis = par2.get_grid_helper().new_fixed_axis
      par2.axis["right"] = new_fixed_axis(loc="right", axes=par2, offset=  
      (offset, 0))
  
      par2.axis["right"].toggle(all=True)
  
     # host.set_xlim(0, 2)
      #host.set_ylim(0, 2)
  
      host.set_xlabel("Depth")
      host.set_ylabel("Temperature")
      par1.set_ylabel("Salinity")
      par2.set_ylabel("Velocity")
      x  = np.array([0,5,10,15,20,25,30,35])
      y1 = np.array([30.340,30.080,29.116,28.395,28.093,28.040,27.975,27.872])
      y2 = np.array([33.130,34.046,35.119,34.933,34.764,34.824,34.860,34.852])
      y3 = np.array([1544.296, 1544.787, 1543.452,1542.280,1541.522,1544.548,1541.523,1541.368])
  
      p1, = host.plot(x, y1, label="Temperature")
      p2, = par1.plot(x, y2, label="Salinity")
      p3, = par2.plot(x, y3, label="Velocity")
  
      #par1.set_ylim(0, 4)
      #par2.set_ylim(1, 65)
  
      host.legend()
  
      host.axis["left"].label.set_color(p1.get_color())
      par1.axis["right"].label.set_color(p2.get_color())
      par2.axis["right"].label.set_color(p3.get_color())
  
      plt.draw()
      plt.show()
  </code></pre>