Lately I’ve been doing a lot of work with data visualization and learning how to use the Protovis JavaScript library. Here is an example that I have been working on of a Dorling Cartogram. This Dorling Cartogram encodes the size of the national parks as the size of the circle; and the percentage of attendance as the circle’s color. The National Park data comes from The National Park Service Public Use Statistics Reports. It is based on the Dorling Cartogram example from the Protovis examples. The circles are roughly positioned based on the National Park’s geographic location. The attendance figures come from 2009, I hope to update the map once the data for 2010 is complete.
See the example here: National Park Dorling Cartogram
You can get the source code on github.