05 July 2013

Defending Pie Charts?

Well, if the conclusion is that one should never, ever, under pain of ridicule use some means of communication, then, of course, the conclusion will generate exceptions. I have several times
noted here that pie charts generally are a poor way of communicating data. And since they are popular, one defensible rhetorical strategy is to advocate a total ban. In any case, here are the folks advocating a more lenient approach [1] [2] [3].  A couple of things seem important to this debate. The first is that the focus (as in Tufte) should be on the pragmatics of data graphics - what do we use them for? And what will others try to use them for? If they are mostly or generally obscurantist, then a general skepticism might well be warranted. Second, if (again, like Tufte) your aesthetic runs to the minimalist, then pie charts, which to be useful and clear tend to require considerable amounts of text, will be problematic. So, here is one example a defender presents of a 'good' pie chart:

 I appreciate the message (substance) and the presentation here. But notice that it requires a lot of words. And the grey slice at the bottom remains unlabeled it is incomplete. In that it is much like the defenses of pie charts.

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