title: R ggplot stat_summary: how to include a count of NAs in legend?
body: <p>I am trying to plot one discrete variable on the x-axis against a continuous one on the y. Imagine in mtcars that I am trying to plot cyl vs. disp. What if some of the values of disp were NA? I would like to know how many NA there were for each value of cyl, and to display this in a simple table, possibly right below the legend (or within the legend itself). Is there a simple (or a complicated) way to do this?</p>
  
  <p>Similar and related question I posed: <a href="https://stackoverflow.com/questions/26452364/r-looking-at-means-by-subgroup-and-overall-on-a-line-graph/26452529#26452529">R - looking at means by subgroup and overall on a line graph</a></p>
  
  <p>Thanks!</p>