Common Mistakes In Data Visualization
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Common Mistakes In Data Visualization

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  • Interestingness: relevant, meaningfull, new Function: easiness, usefulness, useability, fit Form: beatty, structure, appearance Integrity: truth, consistency, honesty, accuracy Interesting + function = experiment Function + form = sketch Form + integrity = eye-candy Integrity + interesting = proof of concept Not interesting = boring Not functional = useless No form = ugly No integrity = rubbish

Common Mistakes In Data Visualization Common Mistakes In Data Visualization Presentation Transcript

  • Common mistakes in data visualization Amedee Van Gasse BarCampGhent3 19 December, 2009
  • $ whoami
    • Current day job:
    • MS Office/VBA specialist
    • Desktop & Mail Security (Antivirus, Spam,...)
    • Geek stuff:
    • Ubuntu tweaking
    • Drupal ( http://foutparkeerders.be - with @peterdedecker )
    • Tik vzw ( http://tik.be )
    • [email_address] http://amedee.be http://twitter.com/amedee http://be.linkedin.com/in/amedee http://facebook.com/amedee.vangasse
  • The power of data visualization
    • Chinese proverb: One Picture is Worth Ten Thousand Words
    • The Fast-Food Information Age
    • Pr0n for the stats junk
      • Pointy-Haired Boss
      • Twitter: Infograph of the day ( @bnox )
  • What Makes Good Information Design?
    • Interestingness
    • Function
    • Form
    • Integrity
  • With Great Power...
    • ... Comes Great Responsibility
      • Look for the Hidden Agenda
      • Trust No One
      • Lies, Damned Lies, and Statistics
  • Let's just face it:
  • Why do we lie?
    • Charts, infographics,... are only a simplified representation of a complex reality
    • Compare with maps: they are also (white) lies
    • Used to convice others
    • Because it looks cool
    • Because we don't know any better
  • The axis are (not) your allies
    • Y axis starts at 500. Why 500?
    • Gradients
    • Grey on grey
    • Original chart has animation...
  • Why?
    • December = 1/5 size of January = CRISIS!!!
    • Fear, Uncertainty and Doubt
    • Convince employees of needed budget cuts
    • Or... just blind faith in Excel???
  • What really happened
    • 2008 up to Q3 was an exceptionally good year
    • Yes, there was a crisis, but...
    • We went to 1/2, not to 1/5
    • Excel bug: lowest value on Y-axis is ”magic”...
  • What we saw in the meeting 47.988 47.115 47.385 2008 OB 2009
    • No scale
    • Why start at 40.000? Why not 30.000 or 45.000?
    • 3D adds no value
    versus 2008: - 1,3 % versus OB : + 0,6 %
  • A more accurate version
    • Scale added
    • Starts at 0
    • No 3D
    versus 2008: - 1,3 % versus OB : + 0,6 %
  • You need X-Ray Vision for this one
    • Confession: I made this one
    • What if executed > planned? -> invisible!
    • Better chart: bars (executed) + lines (planned)
  • Pie chart hell
    • I made these too!
    • 3D
    • Gradients
    • Could have been combined with previous chart
  • Combining the two previous charts
  • The donut: evil twin of the pie
    • Psychedelic
    • Hard to compare series
  • Can't get enough pie?
    • Only one thing is worse than one pie: two pies
    • Little information
    • You can tell your story with one chart
  • ”Pies are to scale”
    • Pretty colors
    • 3D: same diameter?Perspective?
  • The Mother of all Pie Charts
    • http://www.slideshare.net/netlash/old-media-vs-new-media
    • Sorry, @netlash , but this one really sucks
    • Why are Greece and Germany the same size?
    • Red = good or bad?
    • Lots of comments on InformationIsBeautiful.net
  • The original chart
    • Boring
    • Ugly
    • Easy to understand
  • By the way, did I already tell you that I really hate pie charts?
  • The only good pie charts Pac Man Pie: @flexyflow
  • Want to see some more silly charts?
  • Spiderman loves this one!
    • Radar chart
    • Hard to read
    • Needs a lot of tweaking
    • Ugly even with perfect data
  • 3D: Manhattan chart
    • You can always go... downtown ♫
  • 3D: unstacked area chart
    • This one comes with X-Ray glasses
    • Can you see S3 (yellow)?
    • Use a 2D line chart!
  • Some practical tips
    • Colors
    • Axes, legend & title
    • Logarithmic scale
  • Colors
    • No gradients in background
    • Background contrasts with objects
    • Use color only when needed
    • Different color = difference of meaning in data
    • Soft colors + bright/dark for highlights
  • Colors
    • Stick with a single hue
    • Non-data just visible enough
    • Avoid red+green (colorblind)
    • Leave special effects to Hollywood!!!
  • And the Oscar goes to...
  • Axes, legend & title
    • X Axis: Category or Value?
    • Line charts or XY Scatter charts?
    • Zero-based or not?
    • Second Y axis?
    • Good title and axis labels = no legend needed
    • If your chart needs a legend, it is a bad chart
  • Axes gone wrong
    • X axis is time + location
    • X and Y axes ar not linear
    • A (bad) joke from http://graphjam.com
  • Logarithmic scale
    • Nonlinear stimulus-response: 10x pay raise makes you only 2x happier
    • Avoid unless you know what you are doing
    • Can't be used with 0 in data
    • Use a trick: add 0.001
  • General tips
    • What is your message?
    • Who is your audience?
    • Prepare your data
    • Don't have blind faith in your software
  • Links http://peltiertech.com/WordPress/category/chart-busters http://chandoo.org/wp/category/visualization/ http://graphjam.com/ http://www.informationisbeautiful.net/ http://www.smashingmagazine.com/2009/09/11/ 25-useful-data-visualization-and-infographics-resources/ http://www.smashingmagazine.com/2007/08/02/ Data-visualization-modern-approaches/