Visualizing Change over Time Using Dynamic Hierarchies: TreeVersity2 and the StemView

Abstract

To analyze data such as the US Federal Budget or characteristics of the student population of a University it is common to look for changes over time. This task can be made easier and more fruitful if the analysis is performed by grouping by attributes, such as by Agencies, Bureaus and Accounts for the Budget, or Ethnicity, Gender and Major in a University. We present TreeVersity2, a web based interactive data visualization tool that allows users to analyze change in datasets by creating dynamic hierarchies based on the data attributes. TreeVersity2 introduces a novel space filling visualization (StemView) to represent change in trees at multiple levels--not just at the leaf level. With this visualization users can explore absolute and relative changes, created and removed nodes, and each node's actual values, while maintaining the context of the tree. In addition, TreeVersity2 provides overviews of change over the entire time period, and a reporting tool that lists outliers in textual form, which helps users identify the major changes in the data without having to manually setup 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, or eBay. Our case studies demonstrated that TreeVersity2 is flexible enough to be used in different domains and provide useful insights for the data owners. A TreeVersity2 demo can be found at https://treeversity.cattlab.umd.edu.

Cohort Comparison of Event Sequences with Balanced Integration of Visual Analytics and Statistics

“…He proposed two methods of tree comparison: icicle plot and hierarchical sorting, but does not propose any statistical comparison technique, and focuses more on "leaf-to-leaf" matching, which considers whole paths (or sequences) only. TreeVersity2 [24] compares by tree structure and the node values. Though TreeVersity2 is general to all trees, it leaves out temporal-specific analysis such as duration of or between interval events.…”

Using visualizations to monitor changes and harvest insights from a global-scale logging infrastructure at Twitter

“…Another thread of work focuses on making comparisons, which can be categorized according to complexity factors of the differences [12]: T -topological changes (added/removed nodes, moved subtrees), Vnode value changes, and I -whether the interior nodes' values are independent from their children's values. One group of work focuses on comparing only topological changes (T ).…”

“…The Map of the Market [40] represents stock market price changes using color-coded treemaps. Recently, StemView [12] was developed to support all types of value changes and to provide partial support for topological changes, showing only added/removed nodes but not subtree movements (t +V + I). Scribe Radar (Section 4) falls into the same class (t +V + I).…”

“…We had also considered StemView [12], an icicle-based visualization that adds more visual encodings for displaying changes. However, the downside is that the visualization is less explicit in showing hierarchical structure and requires additional explanation.…”

Disperse: Enabling Web-Based Visualization in Multi-screen and Multi-user Environments

“…As a result, developers frequently build visualizations comprised of multiple linked views of the data, each designed to address a unique set of questions or contexts. This approach has been widely adopted in both research [4,12,23] and industry [29,32,35].…”