title: Scatterplot on top of line plot ggplot
body: <p>Example data:</p>
  
  <pre><code>set.seed(245)
  cond &lt;- rep( c("control","treatment"), each=10)
  xval &lt;- round(10+ rnorm(20), 1)
  yval &lt;- round(10+ rnorm(20), 1)
  df &lt;- data.frame(cond, xval, yval)
  df$xval[cond=="treatment"] &lt;- df$xval[cond=="treatment"] + 1.5
  </code></pre>
  
  <p>I would like the "treatment" condition be plotted as a line and the "control" data be plotted as a scatter plot. So far, I have found a work around where I specify them to both be lines but chose that the control line be plotted as 'blank' in scale_linetype_manual:</p>
  
  <pre><code>plot &lt;-ggplot(data=df, aes(x=xval, y=yval, group=cond, colour=cond))+
  geom_line(aes(linetype=cond))+
  geom_point(aes(shape=cond))+
  scale_linetype_manual(values=c('blank', 'solid'))
  </code></pre>
  
  <p>However, there must be a more straightforward way of plotting the control as a scatter plot and the treatment as a line plot. Eventually, I'd like to remove the geom_point from the treatment line. The way it is now, it would remove the its from the control as well leaving me with nothing for the control. </p>
  
  <p>Any insight would be helpful. Thanks. </p>