title: Rotate switched facet labels in ggplot2 facet_grid
body: <p>I would like to plot some barplots on top of each other using facet_grid:</p>
  
  <pre><code>library(ggplot2)
  
  df &lt;- group_by(mpg, manufacturer) %&gt;%
    summarise(cty = mean(cty), hwy = mean(hwy)) %&gt;%
    ungroup()
  
  df &lt;- melt(df, id.vars = "manufacturer")
  
  ggplot() +
    geom_bar(data =df, aes(x = variable, y = value), stat = "identity") +
    facet_grid(manufacturer ~ ., switch = "y")
  </code></pre>
  
  <p>I use the <code>switch</code>argument of <code>ggplot2::facet_grid()</code>to let the facet labels be displayed on the y-axis instead of on top of each facet. Problem is that the facet labels are plotted vertically and therefore cropped. Is there any way to plot the facet -labels horizontally? All the questions I found so far related to rotating the x-axis labels only, not the facet labels.</p>