title: Order discrete x scale by frequency/value
body: <p>I am making a dodged bar chart using ggplot with discrete x scale, the x axis are now arranged in alphabetical order, but I need to rearrange it so that it is ordered by the value of the y-axis (i.e., the tallest bar will be positioned on the left).</p>
  
  <p>I tried order or sort, but result in sort the x-axis, but not the bars respectively.</p>
  
  <p>What have I done wrong?</p>