James Tam

Information Visualization

Concepts covered

What is Information Visualization?

Tufte's Principles for Information Visualization.

Visual Variables.

These lecture notes are a chosen selection from the "Representations" lectures from CPSC 481

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What Is Information Visualization?

Visually representing representing abstract data on a computer in a way that makes it easier to acquire or use the information.

From www.bravenet.com

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Representations

Representation of numbers• Decimal: 123456• Binary: 010001• Roman Numerals: IV

Different representations have different strengths

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Which is the best flight?

depart arriveAC 117 Vancouver - Calgary 7:00 9:00Cdn 321 Vancouver - Calgary 9:00 12:00Cdn 355 Calgary - Montreal 13:30 19:30AC 123 Calgary - Toronto 12:30 16:30AC 123 Toronto - Montreal 16:45 17:30*time zone: +1 van-cal, +2 cal-tor, mtl

length, stop-overs, switches...

7 9 11 13 15 17

10 12 14 16 18 20

Vancouver

8 10 12 14 16 18

AC 117 Cdn 321

Cdn 355AC 123

Calgary

Toronto

Montreal

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Anscombe’s Quartet

N: 11.0mean X’s : 9.0mean Y’s : 7.5standard error of slope estimate: 0.1sum of squares: 110.0regression sum of squares: 27.5residual sum of squares of Y: 13.8correlation coefficient: 0.8r squared: 0.7regression line: Y=3+0.5X

Graphics Reveal the Data

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Principles for Information VisualizationGraphics should reveal the data• show the data*• not get in the way of the message*• avoid distortion*• present many numbers in a small space• make large data sets coherent• encourage comparison between data• supply both a broad overview and fine detail*• serve a clear purpose

note: many visual examples on the following slides are taken from Tufte’s books

E. Tufte Visual Display of Quantitative Information

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Show The Data

# Buffalo

# Adults # calves

# Buffalo

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Not Get In The Way Of The Message

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Avoid Distortion

Ford GM Pontiac Toyota58

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Ford GM Pontiac Toyota

Maintenance cost / year

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Ford GM Pontiac Toyota

Maintenance cost / year

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Broad Overview And Fine Detail

Mutually Exclusive Views

Icewind Dale (Black Isle)

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Broad Overview And Fine Detail

Overlay

Diablo (Blizzard)

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Broad Overview And Fine Detail

Separate Views

Defender (Williams Electronics)

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Broad Overview And Fine Detail

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Broad Overview And Fine Detail

Bederson, B.B. (May 2000) University of Maryland www.cs.umd.edu/hcil/fisheyemenu/

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Visual VariablesPosition

• Changes in the x, y, z location

Size• Changes in length, area or repetition

Shape• Changes in form

Value• Changes in brightness

Orientation• Changes in alignment

Colour• Changes in hue

Texture• Variations in pattern

Motionwww.st-duffer.com

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Visual Variables

Visual variables can affect how you interpret information

• selective is a change in this variable enough to allow us to select things from a group?

• associative is a change in this variable enough to allow us to perceive things as a group?

• quantitative is there a numerical reading obtainable from changes in this variable?

• orderare changes in this variable perceived as ordered?

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Visual Variable: Position

selective

associative

quantitative

order

100

0100

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selective

associative

quantitative

order

Visual Variable: Size

> >> > > >

=4 X

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Selective

associative

quantitative

order

Visual Variable: Shape

>> >> > > >

15 34 105

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Shape

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Visual Variable: Value

selective

associative

quantitative

order < < < < < <

15 34 105

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Visual Variable: Color

Selective

associative

quantitative

order > > > > > > >>

15 13 34 67

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Color

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Encoding

Common advice says use a rainbow scale- Marcus, Murch, Healey

- problems with rainbows

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Visual Variable: Orientation

selective

associative

quantitative

order ? < < <<< < <

15 17 95

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Visual Variable: Texture

Selective

associative

quantitative

order > > > >

45 15 33

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Texture: Vibratory Effects

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Visual Variable: Motion

selective - motion is one of our most powerful attention grabbers

associative – objects moving in unison groups them effectively

quantitative - subjective perception

order

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Motion

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Summary

How the representation of information can effect the ease to which information can be acquired or used?

What are some general guidelines for Information Visualization?

What are Visual Variables?

How can changes in Visual Variables affect how viewers can interpret information?

Which Visual Variables are more effective at different types of visual interpretation tasks?