title: adding empty graphs to facet_wrap in ggplot2
body: <p>I am trying to create 3 plots where all the panels should have the same size, so I thought the solution might be facet_wrap. My problem is, I do don't want the same number of graphs in each </p>
  
  <pre><code>df &lt;- data.frame(group=c(1,1,2,2,2,3,3),
                   name=c('a','b','c','d','e','f','g'),
                   x=c(1,2,3,4,5,6,7),
                   y=c(2,3,4,5,6,7,8))
  ggplot(df, aes(x,y)) + geom_point() + facet_wrap(~ name, ncol=3)
  </code></pre>
  
  <p>The result combines the graphs into a sequential order but I would like to group them by my group column.</p>
  
  <p>So the result I expect is</p>
  
  <pre><code>a b _
  c d e 
  f g _
  </code></pre>
  
  <p>But what I get is </p>
  
  <pre><code>a b c
  d e f
  g _ _
  </code></pre>
  
  <p>Has anyone a suggestion to create a graph like this, maybe by adding empty graphs? I found a other thread <a href="https://stackoverflow.com/questions/18337789/force-facet-wrap-to-fill-bottom-row-and-leave-any-gaps-in-the-top-row" title="Force facet_wrap to fill bottom row &#40;and leave any “gaps” in the top row&#41;">Force facet_wrap to fill bottom row...</a> But I couldn't get it to run in my case.</p>