title: How to plot a line on a biplot made from PCA coeff and score data?
body: <p>I'm creating biplots of PCA data using the coeff and score outputs. I am looking to draw a  line between the furthest points on the biplot. I'm not sure how add a line to the plot without adding it myself (which would be tedious).</p>
  
  <p>I know which 2 points are the furthest away from each other.
  My coeff is a 7x7, but I am using the first 3 columns for the biplot as well as columns 1:3 in my score matrix.</p>
  
  <p>How would I go about plotting a line with either line or plot3 between these 2 points. It seems like it can be done but I am unsure of what data to specify for the line.</p>