Recommended visualization for hierarchical data

On Tue, Jan 12, 2010 at 5:26 PM, Rex C. Eastbourne<rex.eastbourne at gmail.com
   

wrote:
     

Let's say I have data in the following schema that describes the number of
purchases a company has received from each County in the US:

State | County | Purchases
---------------------------------------
NJ | Mercer | 550
CA | Orange | 23
....

I would like to visualize what states contribute the most to the overall
total, and furthermore within those states, what Counties contribute the
most. What are some recommended R visualizations for this type of data? I
created a treemap using map.market from the portfolio library, like the
following:

http://zoonek2.free.fr/UNIX/48_R/g126.png

Although this is an attractive visual, I want something that makes it
easier to compare the relative sizes of components at a glance (hard with a
treemap because rectangles have different aspect ratios). Does anyone have a
recommended alternate visualization?

Thanks!

     

Just to clarify: I made up the above example for simplicity's sake to
illustrate what I meant by "hierarchical" data. My actual data is not
related to maps or geography, so a map-based visualization wouldn't work.