title: How to include "think-cell"-like percentage changes in a waterfall-chart generated in ggplot2
body: <p>I try to establish R as data visualisation tool in my company. A typical graph type used in my department are waterfall charts (<a href="https://en.wikipedia.org/wiki/Waterfall_chart" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Waterfall_chart</a>).</p>
  
  <p>In R, there are some packages and hints for ggplot to generate a waterfall chart (<a href="https://learnr.wordpress.com/2010/05/10/ggplot2-waterfall-charts/" rel="nofollow noreferrer">https://learnr.wordpress.com/2010/05/10/ggplot2-waterfall-charts/</a>), which I used already.</p>
  
  <p>Unfortunately, a common feature for the used waterfall charts are annotations with arrows to indicate the percentage changes within the steps.</p>
  
  <p>See an example below:</p>
  
  <p><a href="https://i.stack.imgur.com/13yaF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/13yaF.png" alt="Percentage Change Annotations to a Bar / Waterfall Chart"></a></p>
  
  <p>Or here in this video (<a href="https://www.youtube.com/watch?v=WMHf7uFR6Rk" rel="nofollow noreferrer">https://www.youtube.com/watch?v=WMHf7uFR6Rk</a>)</p>
  
  <p>The software used to produce such kind of plots is think cell (<a href="https://www.think-cell.com/" rel="nofollow noreferrer">https://www.think-cell.com/</a>), which is an add-on to Excel and Powerpoint.</p>
  
  <p>The problem I have is that I don't know how to start to tackle the topic. My first thoughts are going in this direction:</p>
  
  <ul>
  <li>Use geom_segment for generating the arrows and boxes</li>
  <li>Use ggplot's annotate funktion to place the text at the arrows or in the boxes</li>
  <li>Calculate the positions automatically based on the data provided to the waterfall chart.</li>
  </ul>
  
  <p>May I ask you, if you have additional thoughts/ideas to implement such graphs in ggplot?</p>
  
  <p>Best Regards Markus</p>