Treemaps, a form of graphics that's turning heads in the data-visualization world, don't look like trees at all. They look more like an aerial view of farm plots, using squares of varying sizes and colors to visually represent data variables.

In a treemap representing the results of a consumer survey of several dozen TV brands, each square represents a product, with its color indicating how that product performed in the survey--green for those with the highest grades, red for those with poor grades, and yellow for those in the middle. The size of each square can represent another variable, such as the product's price or market share. With a glance, a market researcher can quickly see correlations between, say, consumer satisfaction and market share.

Treemaps also let a user click on a specific square to drill down to the underlying data, and, in large-scale treemaps, zoom in on a few squares.

The U.S. Marine Corps uses a series of treemaps called the Marines Equipment Readiness Information Tool to track maintenance and readiness data for all Marine Corps equipment except aviation systems. The main map uses color coding to display the status of 192 weapons systems, and users can drill down into the details to see the status of a needed part. "Readiness is our return on investment," says Michael Williamson, department director for studies and analysis at the Marine Corps logistics command. The system also makes it easy to analyze repair costs and maintenance rates for specific types of equipment, he says.

The Marines began working with treemaps in late 2002 using Honeycomb software from the Hive Group Inc. and an Oracle database to provide a single view of data in a dozen supply and maintenance IT systems. Before that, paper and spreadsheets were used to reconcile the data and prepare readiness reports. The treemap system has about 3,000 users.

Treemaps were invented in the early '90s by University of Maryland computer-science professor Ben Shneiderman, who sits on the Hive Group's board of directors. Now major vendors are taking greater notice of treemaps' potential. Microsoft's community technologies group developed a treemap plug-in for Excel for its own use and earlier this year began offering it for free. Oracle's advanced user-interfaces organization also is experimenting with the technology.

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