title: R ggplot - adding all data points to all facets
body: <p>until now I can't find an appropriate answer, here is my short question about ggplot2 in R:    </p>
  
  <pre><code>data(mtcars)
  ggplot(data=mtcars, aes(x=mpg, y=wt, fill=factor(cyl))) +
  scale_fill_manual(values=c("red","orange","blue"))+
  geom_point(size=2, pch=21)+
  facet_grid(.~cyl)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/Prbzs.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Prbzs.png" alt="enter image description here"></a></p>
  
  <p>This is all fine, now I want all data points (regardless what number cyl has) in every facet (e.g. with a smooth grey below the points)?</p>
  
  <p>Thanks, Michael</p>