In the previous post I briefly described an application based on a type of visualization called a Treemap. They are definitely a useful technique in the right context but after exploring them a bit I found the generated images a bit unsatisfying. The things that I dislike about them are:
Problems 2 & 3 are nicely addressed by a variation which Kai Wetzel calls a Circular Treemap. This design has the obvious drawback that the visualization is no longer space-filling - you can't fit as much information into the same area as with the standard rectangular treemap.
Another variation that occurred to me which sacrifices some information density for perhaps a more natural form is what I have called a 'Multi-Level Pie Chart'. I created an implementation of this technique and found it a reasonably satisfying approach for visually exploring hierarchical data. I'll describe it in detail in a future post. If you just can't wait any longer then you can get some flavour of the idea by investigating the Sunburst Project from Georgia Tech.