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Guerra Gomez, J., Pack, M., Plaisant, C., Shneiderman, B. (May 2013)
Visualizing changes over time in datasets using dynamic hierarchies
Published in IEEE Trans. Visualization and Computer Graphics, 19, 12 (2013), 2566-75

To analyze datasets like the US Federal Budget or the number of students in a University it is common to look for changes over time. This task can be easier and more fruitful if the analysis is performed by grouping by attributes, such as by Agencies, Bureaus and Accounts for the Budget or by Ethnicity, Gender and Major in a University. We present TreeVersity2, a web based interactive data visualization tool that allows users to analyze changes in datasets by creating dynamic hierarchies based on the data attributes. TreeVersity2 introduces a novel space filling visualization designed to represent changes in trees, that showcase the change on all tree levels, not only the leaves. With this visualization users can explore absolute and relative changes, created and removed nodes, and each node’s actual values, while maintaining the context. Moreover, TreeVersity2 includes time-based visualizations that provide the context of the each node’s change over time. Finally, TreeVersity2 provides a reporting tool that lists outliers in textual form, which can help users identify what has changed in the data without having to manually setup the filters. We validated TreeVersity2 with 12 case studies with organizations as diverse as the National Cancer Institute, Federal Drug Administration, Department of Transportation, Office of the Bursar of the University of Maryland, and even eBay. Our case studies demonstrated that TreeVersity2 is flexible enough to be used in different domains to reveal useful insights for the data owners. A demo of TreeVersity2 can be seen at

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