Spinning multi-color

New York Times has a great pointer to the Global Warming Art website.  The author Robert Rohde wants to popularize environmental science by visualization of the data.  There are many interesting charts and well worth repeated visits.

These pie charts cry out for some re-dressing:

The pie charts, the colors, the whole works.  Most troubling is that each pie has its own sorting scheme, and because the text labels were not reproduced in the smaller pies, the reader is sent scrambling around to find the right labels.

In addition, these pie charts, as with almost every other pie chart, fail the self-sufficiency test.  Without all the data printed next to each sector, the reader is simply unable to judge the size of each sector.

Further, the aggregate data (larger pie) may not be as relevant after realizing that the smaller pies show very different patterns.  The following junkart version tries to bring out this fact by treating both dimensions (type of greenhouse gas; source of emission) equitably.

While I picked on this particular chart, I must say I support Robert's effort and wish him luck in this very well-intentioned project.

Comments

[a.c.]

I don't understand what's going on in the junkart version. There doesn't seem to be near enough grey in each bar.

[a.c.]

Oh, I guess I see it now. I guess that's proportion of each cell's contribution to the total emissions, not to the column (gas)'s emissions.

[Harlan]

a.c.: yeah, but I think a better way to do it would be to make the width of each column proportional to the column's percentage of the whole. So the CO2 bars would be 8 times wider than the NO2 bars.

[derek]

Sorting shouldn't really have a place in pie charts anyway. Grouping, yes, and sorting within group; but if you think you can line all the groups in a pie chart up in order, then you haven't really got a set of groups suitable for the circular nature of a pie chart, and should go for bars instead.

I guess the exception would be a rock-scissors-paper series, where there is no clear start or end, yet the elements are in a clear order with respect to their neighbors. I can't think of a real-world example just now, though.

[david]

Like a.c. I fail to see how the JunkCharts version passes the self-sufficiency test; it doesn't really convey much information to me at all, really.

[derek]

I think the attempt to show everything as a proportion of 100% makes the dark bars too small, so I'd abandon that. Then the rectangles are too slim amd widely spaced for the dark to be what Bertin called "retinal variables". I'd close up all the visually-active white spaces and just have gray gridlines, and re-order the categories slightly, a bit like this.

[Kaiser]

David: A few things are apparent from the chart, such as Carbon dioxide overwhelms pretty much everything else, that main CO2 emitting sources do not emit other types of gases,that methane and nitrogen oxide are afterthoughts (at least in terms of volume).

Derek: your version looks more attractive. what is the scale you're using? Which part adds up to 100%? I agree with you that the chart can be improved by removing all white space in the interior.

[derek]

Jon, the scale there is about 40% from left to right. I tried 100%, with the baselines at 9% and 9+18%, giving the three components their respective spaces in 9%, 18% and 72%, but as I said about Kaiser's bars, the 100% space in a an unstacked bar of eight components created a vast area (800%) of space, that I felt lacked value.
This way, all the dark areas add up to 100%, and the white areas are 8x40%-100%=220%, enough for space, but of no significance to the total.

But I don't feel 8x100%=800% of space has significance either. Most people wouldn't do that with a regular bar chart, even if it was a bar chart whose components added up to 100%.

[derek]

Not Jon, Kaiser, sorry!

[LoveStats]

Edward Tufte would be proud of this ridiculous chart. It can certainly be nominated to the hall of fame!