common visualization issues & how to fix them
TRANSCRIPT
http://poloclub.gatech.edu/cse6242CSE6242 / CX4242: Data & Visual Analytics
Common visualization Issues &how to fix them
Duen Horng (Polo) Chau Assistant ProfessorAssociate Director, MS AnalyticsGeorgia Tech
Partly based on materials by Professors Guy Lebanon, Jeffrey Heer, John Stasko, Christos Faloutsos
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Student of Edward Tufte
http://a.co/6BhlPfZ
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Edward TufteAn American statistician and professor emeritus of political science, statistics, and computer science at Yale University.
He is noted for his writings on information design and as a pioneer in the field of data visualization.
-Wikipedia
Also Highly Recommended:
5Can you improve its visual design?
6Which is better?
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What can you improve?
Tables
What’s the problem with making everything bold or italic?
“When everyone is super, no one is super”
http://www.youtube.com/watch?v=A8I9pYCl9AQ
“When everyone is super, no one is super”
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A lot of “chart junk”. Low “data to ink” ratio (Edward Tufte)
12Higher “data to ink” ratio
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Problems?
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The color scheme reminds you of what?
Bar Charts
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Better than Christmas(Use color brewer to find good color schemes)
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Company Profits
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Don’t show profits in red!!Think carefully about your color choices.
Company Profits
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Misleading Bar Charts
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Vertical axis of bar charts should start at 0, almost always
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Disorienting color bars
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Use gradation
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Avoid Tilted or Rotated Labels
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Bars Can be Horizontal
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Bars Can be Horizontal
When labels are hard to read, try horizontal layout. Don’t settle for the default.
25http://www.apple.com/imac/performance/
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Line Charts (a.k.a. fever lines)
Can you improve the tick labels?
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Use ticks at common intervals (e.g., 2, 5, 10, etc.)
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Note y-axis does not need to start at 0. Why not as bad as in the case of bar chart?
Too flat or too steep?
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Rule of Thumb
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Multiple Patterned Lines in one chart
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Which one is more effective? Why? What if you have many lines you want to show?
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“Small Multiple” - Edward Tufte Better than overlapping (sometimes)
“a series or grid of small similar graphics or charts, allowing them to be easily compared”
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The Dreaded Pie Charts
Why people like to use pie charts?
34http://www.wired.com/2008/02/macworlds-iphon/
35http://flowingdata.com/2012/06/15/what-3-d-pie-charts-are-good-for/
36http://wonkette.com/412361/all-193-of-republicans-support-palin-romney-and-huckabee
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38http://infosthetics.com/archives/2008/09/funniest_pie_chart_ever.html
Log scale instead of linear scale Include numbers from different orders of magnitude
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Example
log-log
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Example“log” also works well for time
In-class Exercise.Applying what you have just learned.
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How to fix the defaults
43http://www.darkhorseanalytics.com/blog/clear-off-the-table
How to fix the defaults
43http://www.darkhorseanalytics.com/blog/clear-off-the-table
Great Work destroyed by Poor Presentation
Bad color schemesBad, tiny fontsToo much animationToo much data
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100 times faster!
http://www.youtube.com/watch?v=lpvgfmEU2Ck&feature=player_embeddedDon McMillan: Life After Death by PowerPoint
can you read this?
Practitioners’ GuideColors: start with black & white Forces you to focus on content and layout
Then add colors, carefully
Fonts: sans-serif generally easier to read On Mac: Helvetica is great start On Windows: Arial?
Animation: start with no animation, then add meaningful ones
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Practitioners’ Guide: Use Pictures and Videos
“Pictures” include tables, diagrams, charts, etc.• Pictures often more succinct & memorable• People like pictures and love movies
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And show them ASAP! Once people fall asleep, it’s hard to wake them up!
If you have good stuff, show them now.
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Example
Practitioners’ Guide: Additional Tips for PhD students / Researchers
Crown-jewel pictures are important
• Overview of what readers is going to get — cut to the chase
• People skim; look at “interesting” things first
• Reviewers are busy and sleepy 😴 (read 5-10 papers per conference) — it’s refreshing to read an interesting paper
How to do it?
• Use your most impressive figure
• Can be similar to another shown later
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Figures should be self-contained.
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50http://www.cs.cmu.edu/~dchau/polonium_sdm2011.pdf
Example
Figures should be self-containedWhy?• Don’t make people go back
and forth between text & figure
• Bad figures means bad first impression (reject!)
How to fix?• Succinctly describe your
main (take-away) messages
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Example
Use legible fonts.
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For printed materials, print them out and check!Rule of thumb: about 7 lines of text on a slide.
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If people can’t see it, they won’t appreciate it.
Apple UI Design Guidelines
55https://developer.apple.com/design/tips/
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Example
Higher is better.Apolo wins.
* Statistically significant, by two-tailed t test, p <0.05
Judges’ Scores
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Model-based
*Prototyping *Average
Apolo Scholar
Score
Example