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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

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Trees

• Hierarchies often represented as trees• Root at top, leaves at bottom

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Sample Representation

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Another Representation

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Another Representation

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Another Representation

root

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Another Representation

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Potential Problems

• Width of fan-out uses real estate− Run out of room quickly

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Another Idea

CHEOPS

Beaudoin, Parent & Vroomen

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Another Idea

Card, Mackinlay & Robertson

ConeTree

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Another Idea

• Use hyperbolic geometry• Hyperbolic tree

• Here: Site Lens fromwww.inxight.com

• Demo

Lamping & Rao

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Space-Filling Representation

Each item occupies an area

Children are “contained” under parent

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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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Treemap

• ExampleFile and directory visualizer

white-directoriescolor-files

level 1dirs

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Treemap

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Nested vs. Non-nested Treemaps

Nested Tree-Map Non-nested Tree-Map

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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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Treemap Variation

• SmartMoney.com Map of the Market− Illustrates stock movements− “Compromises” treemap

algorithm to avoid badaspect ratios

www.smartmoney.com/marketmap

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Treemap Variation

• Use 3Dshadingcues tohelpconveystructure

SequoiaViewfile viewer forWindows

Demo

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Another Technique

• 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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Sunburst

Visualizing fileand directorystructures

Root dir at centerColor - file typeAngle - file/dir size

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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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Experiment

• 60 participants• Participant only works with a small or

large hierarchy in a session• Vary order across participants

SB A, TM BTM A, SB BSB B, TM ATM B, SB A

32 on small hierarchies28 on large hierarchies

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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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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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Observations

• SB appeared to convey structure better• Participants felt TM conveyed size better,

but not bore out• Strategies mattered

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SunBurst Negative

• In large hierarchies, files at the periphery are usuallytiny and verydifficult todistinguish

examples

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Fix: Objectives

• 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

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With Eugene ZhangProceedings of Information Visualization 2000,Oct. 2000, pp. 57-65.

3 Solutions

• Three visualization+navigation techniques developed to help remedy the shortcoming− Angular detail− Detail outside− Detail inside

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Angular Detail

• Most “natural”• Least space-efficient• Most configurable by user

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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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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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Video

4 minutes

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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