title: Horizontal barchart with facet_grid, free_x not working
body: <p>Using the <code>mpg</code> dataset as an example, I want to use <code>facet_grid()</code> where the only the relevant models are listed under each manufacturer.</p>
  
  <p>This code seems to work (left chart)</p>
  
  <pre><code>library(ggplot2)
  qplot(cty, model, data=mpg) +
    facet_grid(manufacturer ~ ., scales = "free", space = "free")
  </code></pre>
  
  <p>But this one doesn't (right)</p>
  
  <pre><code>ggplot(mpg) +
    geom_bar(aes(x = model, y = cty), stat = "identity") +
    coord_flip() +
    facet_grid(manufacturer ~ ., scales = "free", space = "free")
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/Xi2af.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Xi2af.png" alt="enter image description here"></a></p>
  
  <p>I saw this thread but couldn't get it to work:
  <a href="https://stackoverflow.com/questions/36424282/horizontal-bar-chart-with-facets">Horizontal bar chart with facets</a></p>
  
  <p>Thoughts?</p>