1. Information Visualization 2 Case 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
Fall 2002
CS/PSY 6750

2. Trees Hierarchies often represented as trees
Root at top, leaves at bottom
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3. Sample Representation
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4. Another Representation
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5. Another Representation
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6. Another Representation
root
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7. Another Representation
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8. Potential Problems Width of fan-out uses real estate
Run out of room quickly
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9. Another Idea
CHEOPS
Beaudoin, Parent & Vroomen
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10. Another Idea ConeTree Card, Mackinlay & Robertson Fall 2002
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11. Another Idea Use hyperbolic geometry Hyperbolic tree
Here: Site Lens from
Demo
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Lamping & Rao

12. Space-Filling Representation
Each item occupies an area
Children are “contained” under parent
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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
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14. Treemap Example File and directory visualizer white-directories
color-files
level 1
dirs
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15. Treemap
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16. Nested vs. Non-nested Treemaps
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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
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18. Treemap Variation SmartMoney.com Map of the Market
Illustrates stock movements
“Compromises” treemap algorithm to avoid bad aspect ratios
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19. Treemap Variation Use 3D shading cues to help convey structure Demo
SequoiaView file viewer for
Windows
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20. Another Technique Sunburst
What if we used a radial rather than a rectangular space-filling technique?
Sunburst
Demonstration of system
/usr/local/bin/sunburst
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CS/PSY 6750

21. Sunburst Visualizing file and directory structures Root dir at center
Color - file type
Angle - file/dir size
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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) A B A B
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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
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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)
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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)
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26. Observations SB appeared to convey structure better
Participants felt TM conveyed size better, but not bore out
Strategies mattered
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27. SunBurst Negative
In large hierarchies, files at the periphery are usually tiny and very difficult to distinguish
examples
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28. Fix: Objectives Avoid use of multiple windows or lots of scrollbars
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
Fall 2002
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
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30. Angular Detail Most “natural” Least space-efficient
Most configurable by user
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31. Detail Outside Exhibits non-distorted miniature of overview
Somewhat visually disconcerting
Focus is quite enlarged (large circumference and 360°)
Relatively space efficient
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32. Detail Inside Perhaps least intuitive and most distorting
Items in overview are more distinct (larger circumference)
Interior 360° for focus is often sufficient
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33. Video
4 minutes
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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
Fall 2002
CS/PSY 6750