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Infographics: The great circle debate

The views expressed are those of the author and are not necessarily those of Scientific American.

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If you’re ever at a loss for conversation amid a group of information-graphics professionals, bring up the topic of pie charts or proportional circles. Then stand back and watch the sparks fly. At the World Infographics Summit in Pamplona, Spain, this past week, the love/hate relationship with circular data presentations was a common theme.

Purists, such as Stephen Few (founder and principal, Perceptual Edge) and John Grimwade (graphics director, Conde Nast Traveler) are wary of the functionality of circle-based charts. Indeed, the human brain is more adept at comparing lengths than areas. For example, the largest wedge in this pie chart is clearly identifiable (figure 1). But what is the second largest category? And the third? A bar chart–even without a background grid–is easier to read.

Others, such as Alberto Cairo (director for infographics and multimedia at Época-Editora Globo), worry that bar and line charts have become too familiar, and risk being overlooked or dismissed too quickly by the reader. These standard visualization formats are indisputably elegant solutions, but information-graphics professionals should not rest on their haunches and rely too heavily on a form established in the late 1700s. Instead, we should push the boundaries and explore new ways of presenting the data in an effort to better engage the reader. Perhaps it was in this spirit that the proportional circle chart was born.

I have certainly been seduced by the format. Back in the July 2010 issue of Scientific American, I used proportional circles to provide perspective for the Deepwater Horizon oil spill (figure 2). I think it was an effective solution. But readers need to take a leap of faith when faced with these sorts of charts. Is the data properly represented in terms of relative areas of the circles? Or was the data used to inform the relative diameters of the circles? This representation would result in a dramatically different and misleading chart.

Part of the appeal in using proportional circle charts lies in their flexibility. The designer is released from using axis lines, and is given the freedom to use data points as design elements on the page. Although often visually pleasing, it may do a disservice to the data. Take this example (figure 3). The two central circles are the same size, but our perception is distorted by the surrounding elements. Chart makers can control exact measurements. But what about perceived measurements?

In my opinion, context is key. I would hope that my doctor relies on excruciatingly clear and straightforward–if boring–data displays. Yet readers of Scientific American magazine may be better served by more engaging and dynamic charts. The trick lies in approaching every chart thoughtfully, with the goal of allowing the data’s story to outshine its container.

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  1. 1. odyssoma 8:17 pm 03/29/2011

    The "trick" is not working for your publication. Increasingly, I find Scientific American’s images to be more about glitz ("engaging and dynamic") than information. Too pretty, and not enough data. The space and resources could be better used. I say this regretfully, after more than 40 years as a reader.

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  2. 2. albertocairo 5:03 am 03/30/2011

    I usually don’t comment on articles that quote me, but I feel compelled to do it here: I love line and bar charts! It is true I am in favor of using new graphic forms, but also that I am a form-depends-on-functions person: any graphic form should be chosen based on the tasks the graphic is intended to facilitate.

    Infographics and visualizations are tools, aids for understanding, and they should be designed as such: they can (and should) be pretty, but not just for the sake of being pretty, but because beauty, when it doesn’t hurt functionality, makes your use experience better (ask Apple fans about it). You should not choose a novel graphic form just because it looks cool.

    Regarding bubble charts, I like proportional symbol maps, but bubbles are always inferior to bars when it comes to accurate comparisons of quantities, so they are a poor choice if the thing you need is a bar chart. I have written about it here (in Spanish):

    When I said infographics professionals should not rely so much on hunches I was proposing that they rely more on research, meaning that we all should study more cartography, statistics and cognitive psychology, to base our decisions on how the eye-brain system works. And to inform our decisions on when to use an innovative kind of graphic.

    Thanks for the article, Jen.

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  3. 3. Quinn the Eskimo 1:50 am 03/31/2011

    Finally, I’ve been reading SciAm since the late 60′s! Now, after all these years, SciAm has seen fit to discover the …

    ROUND TUIT! Whew!

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  4. 4. jchristi 5:53 am 03/31/2011

    Thanks for clarifying your viewpoint, Alberto!

    I did not intend to imply that you eschew bar and line charts all together, but simply to highlight that you spoke of reaching beyond those styles when appropriate. As with all of the designers referenced in the original blog post, this was not an attempt to define anyone else’s singular overarching philosophy, but simply to highlight various points made during their presentations at Malofiej last week, and how I internalized those points in an attempt to articulate my own philosophy towards data visualizations in particular.

    I encourage interested readers to check out the links embedded in the original post for a more complete representation of the specific designers referenced.

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  5. 5. odyssoma 9:16 pm 03/31/2011

    I would like to withdraw my previous acerbic comments as they may relate to Jen Christiansen, whose data-based graphic work is first rate. I should have been more circumspect, and directed my complaint to the editorial decisions to favor conceptual, rather than informative, graphics in many of the Scientific American articles.

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