title: Clusters labels in dendrogram
body: <p>I'm wondering - is there any way how to add labels of clusters into dendrogram. See simple example:</p>
  
  <pre><code>hc = hclust(dist(mtcars))
  plot(hc, hang = -1)
  rect.hclust(hc, k = 3, border = "red")
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/QwMbI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QwMbI.png" alt=""></a></p>
  
  <p>Desired output should look like this:</p>
  
  <p><a href="https://i.stack.imgur.com/UeQoK.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UeQoK.png" alt=""></a></p>
  
  <p>Thanks for any suggestions!</p>