title: Principal Components Analysis biplot in R with convex polygons
body: <p>I’ve  produced attached biplot using the following code:</p>
  
  <pre><code>dd = data.frame(x = runif(10), y=runif(10)) 
  pcr = prcomp(~x + y, data=dd)
  biplot(pcr)
  </code></pre>
  
  <p>This produces a biplot showing the axis for x and Y and each of the 10 data points. </p>
  
  <p>Lets say that the 10 data points are made up of 2 different groups, (5 in one group, 5 in the other group). How can I produce a biplot with a Minimum Convex Polygon around each group, to show a division for the 2 groups?</p>