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How (not) to lie with
visualization
cs5984: Information Visualization
Chris North
Final Quiz
• 7 information types:
•
•
•
•
•
•
•
1d
2d
3d
Multi-d
Trees
Graphs
Doc collections
Where are we?
Information Types:
• Multi-D
• 1D
• 2D
• Hierarchies/Trees
• Networks/Graphs
• Document collections
• 3D
Topics:
• Design Principles
• Empirical Evaluation
• Java Development
• Visual Overviews
• Multiple Views
• Peripheral Views
• Workspaces
• Debates
• Vis. Lies
How (not) to lie with
visualization
• Show and tell
• “USA Today” graphs…
Stock Market Crash?!
Market
$9000
8875
8750
8625
8500
1995
1996
1997
1998
1999
2000
Show entire scale
Market
$10,000
7500
5000
2500
0
1995
1996
1997
1998
1999
2000
Show in context
Market
$10,000
7500
5000
2500
0
1950
1960
1970
1980
1990
2000
Another example
Percentages: 0% – 100%
Employment rate = 100 – unemployment rate
Tufte’s Rule
• Visual attribute value should be directly
proportional to data attribute value
• Lie factor = (visual effect) / (data effect)
• truth = 1.0
Company financial status
The hidden 0-points
• Lie factor = ?
Changing Scale
0.5?
13
Changing
Scale
…with linear time scale
Down = Bad ?
Make it explicit
Other examples: user performance, questionnaire results
Logarithmic data  log scale
Size Coding
Size Coding: width or area?
=
?
Size Coding
Width or Area
• Width = value
Height = value
Area = value2
or
• Area = value
width*height = value
width = height = value 0.5
Problem:
Using 2 dimensions to
represent 1 dimension.
Volume coding?
Height?
Diameter?
Surface area?
Volume?
73 – 79 data difference = 5.5x
73 – 79 volume difference = 270x
Problem with area encoding
1
Width
Area
Volume
2
3
4
5
6
7
Width & height encoding
1
Width
Width & Height
2
3
4
5
6
7
Solution: just use width (or height)
A Propaganda Classic
Hmmm…
•
•
•
•
Low rank = good!
Different time scales
Not really tuition
Artistic mood
How not to lie
• Show entire scale
• Show data in context
• Consistent, linear scale
• Log scale for log data
• Up vs. down: indicate direction of improvement
• Avoid size coding
• Use width OR height
• Don’t use both for same data attribute
• Avoid area coding
Visualization = Communication
• Communication is person dependent
• People have a lot of “baggage”
Expectations
Life
is a
a highway
Paris
in the
the spring
Now
is the
the time
Re-training
• Red spades, black hearts
• Poor user performance even after being told
Orientation
• Who are they?
Orientation
Homework 3 Results
• Hinite bites.
• Too much hypertexty stuff
• Not enough zooming, infovisy stuff
• Keep trying to break out of the box!
• Visualization in the periphery - evaluation
» David, Christa, Ali, Jon
Projects
• Visualizing Multi-D functions
» Reenal, Priya, Mrinmayee
• Visualization of data structures – evaluation
Dec 4
» Kunal, Vikrant, Anuj
• Snap-together visualization
» Rohit, Varun, Jeevak, Atul
• Visual Break-down analysis with Financial data
» Ganesh, Anusha, Muthukumar, Sandeep
• Human-eye view
Dec 6
» Alex, Qiang, Ming, Vishal, Ahmed
• Bioinformatics
» Quoc, Mudita, Dhananjay
• Online chat/video-conference visualization (virtual school)
» Mahesh, Ben, Samal, Kuljeet, Harsha, Parool
• Digital libraries
» Jun, Supriya, Abhishek, Anil
• Maps and in-vehicle interfaces
» Ying, Xueqi, Zhiping, Rui
Dec 11
Your Last InfoVis Assignment!
• Dec 18: Project Final Paper due
• Dec 7: ACM CHI short papers due
• Other destinations:
• March?: IEEE InfoVis papers due
•…