title: R: multiple x axis with annotations
body: <p>Is it possible to add more than one x-axis to a plot in R? And to put an annotation next to each scale?</p>
  
  <p>Edit > here's the result of Nick Sabbe idea. For the annotation (a little text at the left of each axis), is it possible ?</p>
  
  <p><img src="https://i.stack.imgur.com/Hlmye.jpg" alt="enter image description here"></p>