This chart was inspired by Facebooks heatmap-esque visualisation for determining what computers (though it doesn't have to be computers) are either malfunctioning or sending alerts. In a large datacenter each column could be a particular rack and each individual square a specific computer.
Each individual square is a drawing API Rect object - so they can be assigned their own tooltip, colors and click/mousemove events.
This goes in the documents header:<script src="RGraph.common.core.js"></script> <script src="RGraph.common.dynamic.js"></script> <script src="RGraph.common.tooltips.js"></script> <script src="RGraph.drawing.rect.js"></script> <script src="RGraph.bar.js"></script>Put this where you want the chart to show up:
<canvas id="cvs" width="600" height="250">
[No canvas support]
</canvas>
This is the code that generates the chart: