common visualization issues & how to fix them · better than christmas (use color brewer to...
TRANSCRIPT
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http://poloclub.gatech.edu/cse6242
CSE6242: Data & Visual Analytics
Common visualization Issues &
how to fix them
Duen Horng (Polo) Chau Associate Professor, College of ComputingAssociate Director, MS AnalyticsGeorgia Tech
Mahdi Roozbahani Lecturer, Computational Science & Engineering, Georgia TechFounder of Filio, a visual asset management platform
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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Also Highly Recommended:
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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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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
When labels are hard to read, try horizontal layout.
Don’t settle for the default.
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http://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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Better? Note the “double encoding” of line width and brightness.
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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What can you improve?
Tables
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What’s the problem with
making everything
bold or italic?
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“Everyone is special” ➞ “No one is”
https://youtu.be/1E9pKU_N15A
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When everyone is special, no one is!
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A lot of “chart junk”.
Low “data to ink” ratio (Edward Tufte)
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32Higher “data to ink” ratio
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Problems?
Name Data
Company A 1000
Company B 900
Company C 80
Company D 7
Name Data
Company A 10.82
Company B 9.49
Company C 8
Company D 7.4
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Name Data
Company A 10.8
Company B 9.5
Company C 8.0
Company D 7.4
Name Data
Company A 10.82
Company B 9.49
Company C 8
Company D 7.4
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Beautiful Publication-quality LaTeX Tables
https://tex.stackexchange.com/questions/112343/beautiful-table-samples
Short guide: https://www.inf.ethz.ch/personal/markusp/teaching/guides/guide-tables.pdf
Long guide: http://cpansearch.perl.org/src/LIMAONE/LaTeX-Table-v1.0.6/examples/examples.pdf
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The Dreaded Pie Charts
Why people like to use pie charts?
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37http://www.wired.com/2008/02/macworlds-iphon/
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38http://flowingdata.com/2012/06/15/what-3-d-pie-charts-are-good-for/
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39http://wonkette.com/412361/all-193-of-republicans-support-palin-romney-and-huckabee
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41http://infosthetics.com/archives/2008/09/funniest_pie_chart_ever.html
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Log scale instead of linear scaleInclude numbers from different orders of magnitude
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Example
log-log
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Example“log” also works well for time
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In-class Exercise.Applying what you have just learned.
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Can you improve its visual design?
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51Which is better?
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How to fix the defaults
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http://www.darkhorseanalytics.com/blog/clear-off-the-table
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How to fix the defaults
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http://www.darkhorseanalytics.com/blog/clear-off-the-table
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Practitioners’ Guide
Colors: start with black & white, then add colors, carefully
Forces you to focus on content and layout
Fonts: sans-serif generally easier to read
(On Mac: Helvetica is great start)
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
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Example
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Example
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Practitioners’ Guide:
Additional Tips for Researchers
Crown-jewel pictures are important
• Overview of what readers is going to get — cut to the
chase (don’t tease!)
• People skim and 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
Why?
• 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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62http://www.cs.cmu.edu/~dchau/polonium_sdm2011.pdf
Example
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More generally, how to write “good” papers?
63http://faculty.washington.edu/wobbrock/pubs/Wobbr
ock-2015.pdf
http://approximatelycorrect.com/2018/01/29/heuristics-
technical-scientific-writing-machine-learning-perspective/
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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.
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Redesign figures for presentation
Designing for print is different from designing for
the screen
• Resolution (which is higher?)
• Levels of details (people mostly want a few
“take-away” messages from your talk)
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Example
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Higher is better.
Apolo wins.
* Statistically significant, by two-tailed t test, p <0.05
0
8
16
24
Model-based
*Average
Judges’ ScoresApolo Scholar
Score
Example
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Great Work destroyed by
Poor Presentation
Bad color schemes
Bad, tiny fonts
Too much animation
Too much data
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100 times faster!
http://www.youtube.com/watch?v=lpvgfmEU2Ck&feature=player_embedded
Don McMillan: Life After Death by PowerPoint
can you read this?