Information Visualization 2 Case Study: Portraying Hierarchies

1. Information Visualization 2Case Study: Portraying Hierarchies • Visualizing hierarchies • Variety of techniques • Traditional tree views, alternatives, space-filling views Hierarchies • Definition • Ordering of items in which particular items are parents or ancestors of others • Example: File System • Folders/Directories with folders/subdirectories and files inside CS/PSY 6750

2. Trees • Hierarchies often represented as trees • Root at top, leaves at bottom CS/PSY 6750

3. Sample Representation CS/PSY 6750

4. Another Representation CS/PSY 6750

5. Another Representation CS/PSY 6750

6. Another Representation root CS/PSY 6750

7. Another Representation CS/PSY 6750

8. Potential Problems • Width of fan-out uses real estate • Run out of room quickly CS/PSY 6750

9. Another Idea CHEOPS Beaudoin, Parent & Vroomen CS/PSY 6750

10. Another Idea ConeTree Card, Mackinlay & Robertson CS/PSY 6750

11. Another Idea • Use hyperbolic geometry • Hyperbolic tree • Here: Site Lens fromwww.inxight.com • Demo Lamping & Rao CS/PSY 6750

12. Space-Filling Representation Each item occupies an area Children are “contained” under parent CS/PSY 6750

13. Treemap • Space-filling representation developed by Shneiderman and Johnson • Children are drawn inside their parent • Alternate horizontal and vertical slicing at each successive level CS/PSY 6750

14. Treemap • Example File and directory visualizer white-directories color-files level 1 dirs CS/PSY 6750

15. Treemap CS/PSY 6750

16. Nested vs. Non-nested Treemaps Nested Tree-Map Non-nested Tree-Map CS/PSY 6750

17. Treemap Affordances • Good representation of two attributes: color and area • Not as good at representing structure • What happens if it’s a perfectly balanced tree of items all the same size? • Also can get long-thin aspect ratios CS/PSY 6750

18. Treemap Variation • SmartMoney.com Map of the Market • Illustrates stock movements • “Compromises” treemapalgorithm to avoid badaspect ratios www.smartmoney.com/marketmap CS/PSY 6750

19. Treemap Variation Demo • Use 3Dshadingcues tohelpconveystructure SequoiaViewfile viewer for Windows CS/PSY 6750

20. Another Technique • What if we used a radial rather than a rectangular space-filling technique? Sunburst • Demonstration of system /usr/local/bin/sunburst CS/PSY 6750

21. Sunburst Visualizing fileand directory structures Root dir at center Color - file type Angle - file/dir size CS/PSY 6750

22. Experiment • Compare Treemap and Sunburst with users performing typical file/directory- related tasks • Evaluate task performance on both correctness and time Small Hierarchy (~500 files) Large Hierarchy (~3000 files) B A B A CS/PSY 6750

23. Experiment • 60 participants • Participant only works with a small or large hierarchy in a session • Vary order across participants SB A, TM B TM A, SB B SB B, TM A TM B, SB A 32 on small hierarchies 28 on large hierarchies CS/PSY 6750

24. Tasks • Identification (naming or pointing out) of a file based on size, specifically, the largest and second largest files (Questions 1-2) • Identification of a directory based on size, specifically, the largest (Q3) • Location (pointing out) of a file, given the entire path and name (Q4-7) • Location of a file, given only the file name (Q8-9) • Identification of the deepest subdirectory (Q10) • Identification of a directory containing files of a particular type (Q11) • Identification of a file based on type and size, specifically, the largest file of a particular type (Q12) • Comparison of two files by size (Q13) • Location of two duplicated directory structures (Q14) • Comparison of two directories by size (Q15) • Comparison of two directories by number of files contained (Q16) CS/PSY 6750

25. Results • Ordering effect for Treemap on large hierarchies • Performance trends favored Sunburst, but not clear-cut • Subjective preference:SB (51), TM (9), unsure (1) CS/PSY 6750

26. Observations • SB appeared to convey structure better • Participants felt TM conveyed size better, but not bore out • Strategies mattered CS/PSY 6750

27. SunBurst Negative • In large hierarchies, files at the periphery are usuallytiny and verydifficult todistinguish examples CS/PSY 6750

28. Make small slices bigger Maintain full circular space-filling idea Allow detailed examination of small files within context of entire hierarchy Don’t alter ratios of sizes Avoid use of multiple windows or lots of scrollbars Provide an aesthetically pleasing interface in which it is easy to track changes in focus Fix: Objectives CS/PSY 6750

29. 3 Solutions • Three visualization+navigation techniques developed to help remedy the shortcoming • Angular detail • Detail outside • Detail inside With Eugene Zhang Proceedings of Information Visualization 2000, Oct. 2000, pp. 57-65. CS/PSY 6750

30. Angular Detail • Most “natural” • Least space-efficient • Most configurable by user CS/PSY 6750

31. Detail Outside • Exhibits non-distorted miniature of overview • Somewhat visually disconcerting • Focus is quite enlarged (large circumference and 360°) • Relatively space efficient CS/PSY 6750

32. Detail Inside • Perhaps least intuitive and most distorting • Items in overview are more distinct (larger circumference) • Interior 360° for focus is often sufficient CS/PSY 6750

33. Video 4 minutes CS/PSY 6750

34. Key Components • Two ways to increase area for focus region: larger sweep angle and longer circumference • Smooth transitions between overview and focus allow viewer to track changes • Always display overview • Allow focus selections from anywhere: normal display, focus or overview regions CS/PSY 6750