title: How to restrict a correlation heatmap to interesting cells and add stars to mark exceptional values?
body: <p>I'm trying to do a nice correlation matrix heatmap in python, but I can't find the options to customize it the way I want.</p>
  <p>My code is simply this one:</p>
  <pre><code>plt.figure(figsize=(16, 6))
  mask = np.triu(np.ones_like(Correlazioni.corr(), dtype=np.bool))
  heatmap = sns.heatmap(Correlazioni.corr(), mask=mask, vmin=-1, vmax=1, annot=True, cmap='BrBG')
  heatmap.set_title('Triangle Correlation Heatmap', fontdict={'fontsize':18}, pad=16);
  </code></pre>
  <p>Now I would like to add (*) in significant cells: ( example: when the coefficient is higher or lower of a certain value)</p>
  <p>Thank you very much for the answers, if I missed anything from my request, please let me know and I will provide it.</p>