title: Changing ylim (axis limits) drops data falling outside range. How can this be prevented?
body: <pre><code>df &lt;- data.frame(age=c(10,10,20,20,25,25,25),veg=c(0,1,0,1,1,0,1))
  g=ggplot(data=df,aes(x=age,y=veg))
  g=g+stat_summary(fun.y=mean,geom="point")
  </code></pre>
  
  <p>Points reflect mean of veg at each age, which is what I expected and want to preserve after changing axis limits with the command below.</p>
  
  <pre><code>g=g+ylim(0.2,1)
  </code></pre>
  
  <p>Changing axis limits with the above command unfortunately causes veg==0 subset to be dropped from the data, yielding </p>
  
  <blockquote>
    <p>"Warning message: Removed 4 rows containing missing values (stat_summary)"</p>
  </blockquote>
  
  <p>This is bad because now the data plot (stat_summary mean) omits the veg==0 points. How can this be prevented? I simply want to avoid showing the empty part of the plot- the ordinate from 0 to .2, but not drop the associated data from the stat_summary calculation.</p>