title: Multiple y-axis conversion scales
body: <p><img src="https://i.stack.imgur.com/GZZ71.jpg" alt="Conversion scale with &#39;parasitic&#39; parallel y axis"></p>
  
  <p><img src="https://i.stack.imgur.com/7N18Q.jpg" alt="Conversion scale with shared y axis"></p>
  
  <p>Hi</p>
  
  <p>I'm trying to create plots which incorporate parallel conversion scales for two sets of units on the y-axis; using the two different styles of:</p>
  
  <ol>
  <li>offset ('parasitic') y-axes and</li>
  <li>overlaid/shared y-axes</li>
  </ol>
  
  <p>to replicate the style of the left-hand y-axes in the attached example images. </p>
  
  <p>I'd like to find the simplest generic way of producing both of the above example plots, which also allows me to generate the y-axis conversion scales by defining the relationship between the two sets of units as a function (in this example: mmHg = kPa * 7.5).</p>
  
  <p>If it's possible to add the third right-hand y axes (vapour concentration and water content) shown in these examples, which are unrelated to the left hand scales, this would be a bonus.</p>
  
  <p>I've read related stackoverflow.com postings and examples on using multiple x and y axes using the twinx and twiny functions - e.g. 
  <a href="https://stackoverflow.com/questions/24325232/two-corresponding-y-axis">here</a> - as well as the Matplotlib cookbook, but I can't find an example which addresses this particular problem.</p>
  
  <p>I'd be very grateful for any minimal working examples or links.</p>
  
  <p>I'm using Matplotlib in Spyder 2.2.1 / Python 2.7.5</p>
  
  <p>Many thanks in anticipation</p>
  
  <p>Dave</p>