title: R - how to make PCA biplot more readable
body: <p>I have a set of observations with 23 variables.</p>
  
  <p>When I use prcomp and biplot to plot the results I run into several problems:</p>
  
  <ol>
  <li><p>the actual plot only occupies half of the frame (x &lt; 0), but the plot is centered on 0, so half of space is wasted</p></li>
  <li><p>two variables clearily dominate the results, so all other arrows are clumped together and I can't read a thing</p></li>
  </ol>
  
  <p>ad 1. I tried setting xlim and/or ylim, but I'm obviously doing something wrong since the plot is all messed up when I do</p>
  
  <p>ad 2. Can I just somehow make the arrow labels placed more apart so that I can read them? Or maybe I could just plot the arrows without the two longest ones (kind of zoom-in)?</p>
  
  <p><img src="https://i.stack.imgur.com/9oT9J.png" alt="My PCA plot"></p>
  
  <p>Addendum: is it possible to have biplot draw the labels in a different color than the arrows?</p>
  
  <p>Also: is it problematic if the x and y axes are not proportional (they graph shows intervals of different length on x and y). 
  I think this would skew the angels between arrows, and that kind of resizing is not a similarity transformation.
  Is it possible to force biplot to keep a 1:1 aspect ratio, or to draw the plot as a rectangle and not a square?</p>