Guess which link-map representation above is the most efficient for showing directionality? Information Aesthetics blog has an interesting article about the different techniques for showing the “from-” and “to-” of network charts.
Networks are often visualized using points and interconnecting lines, with triangular arrowheads at one or both ends to show any directionality between the different points. Although such a standard arrow representation seems intuitive, it can lead to problems in dense graphs that contain many incoming or outgoing relationships. Furthermore, since the arrowheads often have approximately the same size and aspect ratio as the small circles they connect, the graph as a whole might be perceived as cluttered with so much visual detail to the point of being distracting.
via What is the Best Way to Represent Directionality in Network Visualizations? – information aesthetics.
Tree Maps are much more tree-like than Tree Diagrams. Here is another great “R” project from FlowingData blog.
Back in 1990, Ben Shneiderman, of the University of Maryland, wanted to visualize what was going on in his always-full hard drive. He wanted to know what was taking up so much space. Given the hierarchical structure of directories and files, he first tried a tree diagram. It got too big too fast to be useful though. Too many nodes. Too many branches.
The treemap was his solution. It’s an area-based visualization where the size of each rectangle represents a metric since made popular by Martin Wattenberg’s Map of the Market and Marcos Weskamp’s newsmap.
See SmartMoney’s live-updating Treemap of the stock market. (Health care and energy are big movers right now.)
via An Easy Way to Make a Treemap | FlowingData.