title: How do you create a bar plot for two variables mirrored across the x-axis in R?
body: <p>I have a dataset with an x variable and two y1 and y2 variables (3 columns in total). I would like to plot y1 against x as a bar plot above the axis and y2 against the same x in the same plot underneath the x axis so that the two bar plots mirror each other.</p>
  
  <p>Figure D below is an example of what I am trying to do.</p>
  
  <p><img src="https://i.stack.imgur.com/ykaox.jpg" alt="Figure **D**"></p>