title: ggplot: align x-axis with different geoms (ggarrange)
body: <p>I'm using <code>egg::arrange</code> to setup multiple plots and while it is sizing the x-axis correctly for both plots the x-axis values are not aligned.  Easier to explain with an example:</p>
  
  <pre class="lang-r prettyprint-override"><code>data &lt;- data.frame(
    volume=c(100,200,150,400),
    revenue=c(1000,2500,1750,6000),
    day=c(as.Date('2019-10-01'),as.Date('2019-10-02'),as.Date('2019-10-03'),as.Date('2019-10-04'))
  )
  
  p1 &lt;- ggplot(data, aes(x=day,y=volume)) + geom_line()
  p2 &lt;- ggplot(data, aes(x=day,y=revenue)) + geom_col()
  
  egg::ggarrange(p1,p2,nrow=2,heights=c(3,1))
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/EuE9E.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EuE9E.png" alt="arran"></a></p>
  
  <p>The desired output would be each individual day is aligned between plots.  Extra nice would be removing the x-axis entirely from the first plot.</p>
  
  <p>Ideally this would compose with other <code>egg::ggarrange</code> as I'm actually combining a bunch of plots.</p>
  
  <p>Thanks!</p>