(Via Gelman blog)
Prominent marketer Seth Godin came up with some sensible rules for making "graphs that work". We pretty much agree with most of what he says here, unlike the last time he talked about charting.
One must recognize that he has a very specific type of chart in mind, the purpose of which is to facilitate business decisions. And not surprisingly, he advocates simple, predictable story-telling.
His first rule: dispense with Excel and Powerpoint. Agreed but to our dismay, there are not many alternatives out there that sit on corporate computers. So we need a corollary: assume that Excel will unerringly pick the wrong option, whether it is the gridlines, axis labels, font sizes, colors, etc. Spend the time to edit every single aspect of the chart!
His second rule: never show a chart for exploration or one that says nothing. I used to call these charts that murmur but do not opine. (See here, for example.) This pretty much condemns the entire class of infographics as graphs that don't work. This statement will surely drive some mad. One of the challenges that face infographics is to bridge the gap between exploration and enlightenment, between research and insight. As I said repeatedly, I value the immense amount of effort taken to impose structure and clarity on massive volumes of data -- but more is needed for these to jump out of the research lab.
In rules 3 and 4, Seth apparently makes a distinction between rules made to be followed and rules made to be broken. In his view, time going left to right belongs to the former while not using circles belongs to the latter. He gave a good example of why pictures of white teeth are preferred to pie charts, bravo. I hope all those marketers are listening.
As readers know, I cannot agree with "don't connect unrelated events". He's talking about using line charts only for continuous data. This rule condemns the whole class of profile plots, including interaction charts in which statisticians routinely connect average values across discrete groupings. The same rule has created the menace of grouped bar charts used almost exclusively to illustrate market research results (dozens to hundreds of pages of these for each study). I'd file this under rules made to be broken!
Alright, I made my point. If you don't work in market research, the mother lode of cross-tabs and grouped bars, consider yourself lucky. If you do, will you start making line charts please?