title: multi-panel plots in ggplot2: scales that are "free and equal"?
body: <p>I have issued the following command to a ggplot figure:</p>
  
  <pre><code>facet_wrap(~variable,scales="free")
  </code></pre>
  
  <p>but I also want for the x and y scales to be equal for each panel (while the limits vary from panel to panel). Is this possible in ggplot2?</p>