title: adding xticks to subplots in matplotlib
body: <p>I do this</p>
  
  <pre><code>def example_plot(ax, somedata, somedata2, title, xlab, ylab, fontsize=12):
  
      ax.plot(somedata, color='b')
      ax.plot(somedata2, color='g')
      ax.locator_params(nbins=3)
      ax.set_xlabel(xlab, fontsize=8)
      ax.set_ylabel(ylab, fontsize=10)
      ax.set_title(title, fontsize=10)
  
  import matplotlib.pyplot as plt
  import numpy as np 
  fig, ((ax1, ax2), (ax3, ax4)) = plt.subplots(nrows=2, ncols=2)
  ax1.grid(color='r', linestyle='-', linewidth=1)
  ax2.grid(color='r', linestyle='-', linewidth=1)
  ax3.grid(color='r', linestyle='-', linewidth=1)
  ax4.grid(color='r', linestyle='-', linewidth=1)
  
  example_plot(ax1,cumulative1,survival1, t1, xlbl1, ylbl1) 
  example_plot(ax2,cumulative2,survival2, t2, xlbl2, ylbl2)
  example_plot(ax3,cumulative3,survival3, t3, xlbl3, ylbl3)
  example_plot(ax4,cumulative4,survival4, t4, xlbl4, ylbl4)
  
  plt.tight_layout(pad= 0.4, w_pad= 0.5, h_pad = 1.0) 
  </code></pre>
  
  <p>My question revolves around applying custom xticks to every subplot.
  No matter how many times or where I place the lines</p>
  
  <pre><code>plt.xticks(np.arange(0,100, step = 10))
  plt.xlim(0, 100)
  </code></pre>
  
  <p>They only wind up applying to the 4th subplot.
  How to define custom xticks for each subplot?</p>