title: Changing the rotation of tick labels in Seaborn heatmap
body: <p>I'm plotting a heatmap in Seaborn. The problem is that I have too many squares in my plot so the x and y labels are too close to each other to be useful. So I'm creating a list of xticks and yticks to use. However passing this list to the function rotates the labels in the plot. It would be really nice to have seaborn automatically drop some of the ticks, but barring that I would like to be able to have the yticks upright.</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  import seaborn as sns
  
  data = pd.DataFrame(np.random.normal(size=40*40).reshape(40,40))
  
  yticks = data.index
  keptticks = yticks[::int(len(yticks)/10)]
  yticks = ['' for y in yticks]
  yticks[::int(len(yticks)/10)] = keptticks
  
  xticks = data.columns
  keptticks = xticks[::int(len(xticks)/10)]
  xticks = ['' for y in xticks]
  xticks[::int(len(xticks)/10)] = keptticks
  
  sns.heatmap(data,linewidth=0,yticklabels=yticks,xticklabels=xticks)
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/gt6bR.png" alt="enter image description here"></p>