title: how to have x-axis labels in multicolumn ggplot with facet_wrap?
body: <p>When trying to plot something like this:</p>
  
  <pre><code>library(ggplot2)
  d &lt;- ggplot(diamonds, aes(carat, price)) +
    xlim(0, 2) + geom_point()
  d + facet_wrap(~ color)
  </code></pre>
  
  <p>You will notice that the x-axis labels only show up for the first column. I would like them to repeate on the second and third column. Is this possible?</p>
  
  <p>If on the facet_wrap I use the option scales="free", </p>
  
  <pre><code>d + facet_wrap(~ color, scales="free")
  </code></pre>
  
  <p>then i get x-axis labels on all plots, which I also don't want. I want only labels in the bottom row repeating across columns</p>
  
  <p>If the number of panels to be plot is such, that all columns have the same number of plots, the axis gets repeated in the way I want. But I can't always have the right number of panels for that.</p>