He uses this image to demonstrate that people understand better when we measure just changing one dimension (height or width) and not both. And he's right. And we, in Púbico, must recognize the 'mea culpa'. He doesn't say that circles are bad for graphics, we thinks they¡re right when we wnat the reader not the know the exact cypher, but a global vision.
I absolutely agree with Alberto, although I think there's one more reason for using circles: sometimes, with brs, the differences are so extreme tat there are not any possible way to place it on page. This times, circles are easier to place, showing the real difference, and without 'cutting' the bar. I prefer a difference that is not so clear at first sight that one that is 'false'. Anyway, I think is an advice more than needed.
There's another reason to use circles, and I won't recognize I've said this later... Writers and editors like color circles rather than neutral bars. As we stare to paes with puppies and babies. It's not a powerful reason to include this kind of graphics, and we never do it for this reason, but we must recognize that that 'exists'.
PS. TAlking about Alberto Cairo, he release his new infographics book in Spain in September. The bok is calledInfografía 2.0. Visualización interactiva de información en prensa (Inforgraphics 2.0, Interactive visualization of information on newspapers). This is not the book we've already talked about, Visual Journalism, but a good one to keep waiting. Just a problem: would be released just in spanish.
3 comments:
Generally, Alberto is right. But he did not show us what happen, when we have to distribute digit data on area, not on line. For example on map. Bars, which are not aligned are difficult to compare too. That way using circles seems to be more reasonable.
Alberto explains it on his blog, and says that circles on maps are allright, explaining that, usually, they show trends, more than excat data. You can take a look here (although it's in spanish)
http://www.albertocairo.com/infografia/articulos/2008/circulos.html
And thanks for teh comment, Lech!
Good point, Lech. I will try to explain what I meant in my article, which is in Spanish: Circles on maps are a completely different beast than comparison charts, as their goal is to show overall trends, not to allow you to compare each specific magnitude to the contiguous ones. Proportional symbol maps are very powerful and useful to give you "the general picture".
But when it comes to compare numbers, when each number has its own relevance, bar charts are far more powerful than circle ones simply because our brain compares more accurately just one magnitude (width OR height) rather than two (width AND height: surface). This is not an opinion. It is backed by cognitive tests.
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