title: Controlling the tracker when using twinx
body: <p><img src="https://i.stack.imgur.com/ylFS2.png" alt="enter image description here"></p>
  
  <p>The tracker in the lower-right corner (highlighted in red) reports y-values relative to the y-axis on the right. </p>
  
  <p>How can I get the tracker to report y-values relative to the y-axis on the left instead?</p>
  
  <pre><code>import matplotlib.pyplot as plt
  import numpy as np
  
  np.random.seed(6)
  numdata = 100
  t = np.linspace(0.05, 0.11, numdata)
  y1 = np.cumsum(np.random.random(numdata) - 0.5) * 40000
  y2 = np.cumsum(np.random.random(numdata) - 0.5) * 0.002
  
  fig = plt.figure()
  
  ax1 = fig.add_subplot(111)
  ax2 = ax1.twinx()
  
  ax1.plot(t, y1, 'r-', label='y1')
  ax2.plot(t, y2, 'g-', label='y2')
  
  ax1.legend()
  plt.show()
  </code></pre>
  
  <p>I know swapping <code>y1</code> with <code>y2</code> will make the tracker report y1-values,
  but this also places the <code>y1</code> tickmarks on the right-hand side, which is not what I want to happen.</p>
  
  <pre><code>ax1.plot(t, y2, 'g-', label='y2')
  ax2.plot(t, y1, 'r-', label='y1')
  </code></pre>