title: How to draw circle in PCoA results?
body: <p><a href="https://i.stack.imgur.com/Dhk4f.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Dhk4f.png" alt="enter image description here"></a></p>
  
  <p>I have results with <code>PC1</code> and <code>PC2</code> for all the samples, so that I can draw a scatter plot using <code>PC1</code> as x and <code>PC2</code> as y. </p>
  
  <p>Now the samples are labeled by another variable, let's say <code>type</code> indicating which sample is case or control. How can I draw a plot as above, with circles covering the responding <code>type</code>.</p>
  
  <p>Actually, I am using <code>vegan</code> package. I can draw a plot with <code>metaMDS</code> and <code>ordiplot</code>, but don't know how to make a circle as above. I have tried to read the tutorial, but still have no idea.</p>