title: How to rotate x-axis tick labels in a pandas plot
body: <p>With the following code:</p>
  
  <pre><code>import matplotlib
  matplotlib.style.use('ggplot')
  import matplotlib.pyplot as plt
  import pandas as pd
  
  df = pd.DataFrame({ 'celltype':["foo","bar","qux","woz"], 's1':[5,9,1,7], 's2':[12,90,13,87]})
  df = df[["celltype","s1","s2"]]
  df.set_index(["celltype"],inplace=True)
  df.plot(kind='bar',alpha=0.75)
  plt.xlabel("")
  </code></pre>
  
  <p>I made this plot:</p>
  
  <p><a href="https://i.stack.imgur.com/6pLLq.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/6pLLq.jpg" alt="enter image description here"></a></p>
  
  <p>How can I rotate the x-axis tick labels to 0 degrees?</p>
  
  <p>I tried adding this but did not work:</p>
  
  <pre><code>plt.set_xticklabels(df.index,rotation=90)
  </code></pre>