title: Adding bias in Taylor diagram in R
body: <p>I am using the <code>taylor.diagram</code> function in the <code>plotrix</code> package e.g.</p>
  
  <pre><code>obs = runif(100,1,100)
  mod1 = runif(100,1,100)
  mod2 = runif(100,1,100) 
  mod3 = runif(100,1,100) 
  taylor.diagram(obs,mod1)
  taylor.diagram(obs,mod2,add=TRUE)
  taylor.diagram(obs,mod3,add=TRUE)
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/0zDSt.png" alt="enter image description here"></p>
  
  <p>In the conventional Taylor diagram there is no bias but in his paper (Taylor, 2001, K.E. Summarizing multiple aspects of model performance in a single diagram Taylor JGR, 106, 7183-7192) Taylor says that </p>
  
  <p><code>"Although the diagram has been designed to convey information about centered pattern differences it is also possible to indicate differences in overall means (i.e., the bias). This can be done on the diagram by attaching to each plotted point a line segment drawn at a right angle to the straight line defined by the point and the reference point. If the length of the attached line segment is equal to the bias, then the distance from the reference point to the end of the line segment will be equal to the total (uncentered) RMS error"</code></p>
  
  <p>I admit that I don't know where to start to try and do this. Has anyone succeeded at adding this information on the plot?</p>