An over-and-under Bar chart

[No canvas support]

This goes in the documents header: 
<script src="RGraph.common.core.js"></script>
<script src="RGraph.bar.js"></script>
Put this where you want the chart to show up: 
<canvas id="cvs" width="350" height="200">[No canvas support]</canvas>
This is the code that generates the chart: