title: Two y-axes ticks for one set of data, aligning both sets of ticks
body: <p>I have managed to plot y axis tick on the right as a percentage, but the labels aren't to appealing I want to change them to multiples of 10. How do I change the ticks so that they're 10^2% (100%), 10^1%, 10^0%, etc., but that they still match the ticks on the left?</p>
  
  <pre><code>from datetime import datetime
  from dateutil.relativedelta import relativedelta
  from numpy import nan, arange
  import matplotlib
  import matplotlib.pyplot as plt
  from matplotlib.ticker import FuncFormatter
  import sys
  
  twentytwo = {}
  twentytwo[60.0] = [578, 85, 14, 5, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
  
  totNEA2014 = 1266
  
  def to_percent(y, position):
      # Ignore the passed in position. This has the effect of scaling the default
      # tick locations.
      s = str(100 * (y/totNEA2014))
      if matplotlib.rcParams['text.usetex'] == True:
          return s + r'$\%$'
      else:
          return s + '%'
  
  # Plot Details
  bar_width = 0.18
  line_width = 1
  opacity = 1.
  centre_bar_positions = arange(20)
  zeros = [0 for k in range(len(centre_bar_positions))]
  
  # Make bar plots
  fig = plt.figure(figsize=[12, 9])
  ax1 = fig.add_subplot(111)
  bar_60_22 = plt.bar(centre_bar_positions, twentytwo[60.0], bar_width, bottom=10**-1, alpha=opacity, color='green', log=True, label='V &lt; 22')
  
  plt.title("Some Place")
  plt.ylabel("Number of NEAs")
  plt.xlabel("Number of apparitions")
  ax1.set_ylim([ax1.set_ylim()[0], totNEA2014])
  ax1.set_yscale("log")
  plt.legend(loc='best')
  
  ax2 = ax1.twinx()
  ax2.yaxis.set_label_position("right")
  plt.bar(centre_bar_positions, zeros, bar_width, bottom=10**-1, color='white', edgecolor='grey', linewidth=line_width, hatch='0', log=True)
  ax2.set_ylim([ax1.set_ylim()[0], ax1.set_ylim()[1]])
  formatter = FuncFormatter(to_percent)
  plt.gca().yaxis.set_major_formatter(formatter)
  plt.ylabel("Percentage of NEAs discovered in 2014")
  
  plt.xlim([.6, 5.8])
  plt.show()
  </code></pre>
  
  <p>This is what my code currently produces (I reduced the no. of bars in the code above):
  <img src="https://i.stack.imgur.com/5mfXe.jpg" alt="enter image description here"></p>