Tree-Maps: Visualizing Hierarchical Data Hench Qian & Bill Shapiro September 21, 1999

Problem Representing hierarchical data –Structural information –Content information Objectives –Efficient Space Utilization –Interactivity –Comprehension –Esthetics

Favorite Sentence Most people come to understand the content and organization of these structures (hierarchical information) easily if they are small, but have great difficulty if the structures are large.

Traditional Methods Outlines (e.g., Windows Explorer)

Traditional Methods Tree Diagrams (WebView, University of Pittsburg) Text-based tools (e.g., ls in UNIX)

An Alternative: Tree-Maps Problems with traditional methods: –Lots of dead space –Difficult to represent large number of items Tree-Maps –Utilize 100% of display space –Scalable to thousands of items

Tree-Maps

How It Works

Example: TennisViewer

Critique Strengths –Utilizes 100% of display space –Shows relationships between nodes through size and color –Can effectively display large data sets Weaknesses –Size comparison may be difficult –Cluttered display –Difficult to discern boundaries –Shows only leaf content information

Other Hierarchical Visualization Tools Docuverse (University of Pittsburg) –Containers (file directories) are shown as pie segments –Documents (files) are shown as colored dots within pie segments –Can represent a large number of items (~3000) –Utilizes a fraction of the display space

Docuverse -shows 3502 files in 164 directories -pie segments represent # of links to each directory/file -Color represents age of files -shows 3502 files in 164 directories -pie segments represent # of links to each directory/file -Color represents age of files

Other Hierarchical Visualization Tools Hyperbolic Trees (Xerox/Inxight) –Dynamically warps display to zoom in on areas of interest –Good for interactive browsing –Does not provide a good overview of the entire dataset –DemoDemo