Social Science Statistics Blog

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8 November 2007

Beyond scatterplots

Are scatterplots confusing? Turns out the graphics people at the New York Times, who I think have been putting out some outstanding work in the past few years, think so.

Matthew Ericson, Deputy Graphics Editor at the NYT, gave a talk recently at the Infovis conference in which he described some of the techniques his staff uses to communicate information to readers. I wasn't there, but I looked through his slides (70 M zip file), which provide both highlights from the NYT's recent graphics and some indication of the process by which they arrive at a final product. Particularly interesting is the set of slides from 35-62, in which he shows how they developed a graphic depicting partisan shifts between the 2004 and 2006 Congressional elections. Early in the sequence (at page 38), you see a draft of what seems like an adequate approach -- a scatterplot depicting 2004 vote margin vs 2006 vote margin. It turns out (I'm basing this on Fernanda Viegas' description of the talk on the infosthetics blog) that the NYT graphics staff has found that lay readers don't really understand scatterplots, in part because they are so used to seeing time on the x-axis. So Ericson and his staff went back to the drawing board and developed something different (shown on page 61 of the slides; you can also see the a one-page pdf here or by clicking on the thumbnail below). Their new graphic orders the districts vertically by their 2006 vote share and shows the vote outcome on the horizontal axis, depicting the 2004-2006 shift by a horizontal arrow originating at the 2004 vote margin and ending at the 2006 margin. This approach conveys the information much less compactly (for one thing, all of the information in the y-axis is also in the x-axis) but communicates the partisan shift in a more intuitive way, while also giving a better sense of the distribution of partisanship across districts than did the scatterplot. Even though I'm used to seeing scatterplots I think I get a lot more out of this figure, especially with the extra summary stats they are able to depict by continuing on the theme of horizontal arrows depicting 2004-2006 shifts.

Posted by Andy Eggers at 10:55 AM