Perhaps harkening to the close race between Obama and Clinton, the designer chose to illustrate this with what we have called the "racetrack" graph. We have previously discussed the problems here and here.
In this rendition, a pie chart was divided into three race tracks with "cities" getting the inside track and "rural/small cities" getting the outside track. (As the Clinton supporters might say, elitism was in the air.) There were two great choices: the courage to not print the data and let the chart speak for itself, and the wisdom to white out the votes for "others".
Nevertheless, as we discussed before, the data is coded into the angles rather than the lengths of the strips, which presents a real problem in comparing vote shares. For example, try figuring out if there were more Obama supporters in rural Tennessee than there were Clinton supporters in cities in Tennessee (bottom right).
Also note where the white "others" space were, and the impossibliity of comparing them.
The arrangement for Wisconsin, meanwhile, posed a challenge for anyone who wanted to estimate how many rural Wisconsin voters went for "others".
In the junkart version, we go with the two-sided bar chart, typically found in population pyramids. The information presented jumps out at you.
This chart is essentially the same as the racetrack; one just needs to straighten out the strips from the original chart, and pull the Clinton ones clockwise, and Obama ones anti-clockwise.
Reference: some recent issue of New York Times magazine.
Plotting the margins would seem even better, say Clinton margin +ve on right hand side and Obama on left. This would allow quick identification of who was more popular.
Posted by: Ken | Jun 21, 2008 at 08:50 PM
The only piece of chart junk I might add to your two sided bar charts is vertical gridlines at ±50%.
If you used a one-sided clustered bar chart, you could more readily compare the lengths of the Clinton and Obama bars. A little experimentation shows that this helps for comparisons where the two candidates are close (Wisconsin), but is completely worthless when they are far apart (Tennessee).
I've described my charting attempts here:
http://peltiertech.com/WordPress/2008/06/22/close-racesclose-races/
Posted by: Jon Peltier | Jun 22, 2008 at 11:18 AM
That URL came out wrong in my post. It should be:
http://peltiertech.com/WordPress/2008/06/22/close-races/.
Posted by: Jon Peltier | Jun 22, 2008 at 11:21 AM
One of my favorite graph types :-)
I'd only make one comment, which is that I think the cyan is a little too light to easily see, and perhaps I'd prefer a blue or magenta bar instead.
Or, since the bars are physically separate, why not have them be the same color and just label the sides "Clinton" and "Obama"? Different colors could then be used for some other dimension of information, if there was one.
Posted by: derek | Jun 22, 2008 at 12:29 PM
I'd also consider adding the magical 50% treshold (Could it be a background color instead of a vertical line?) as it is a visual piece of information that is lost in the transfer - as is the "others" white space, even with its failures.
Posted by: Markus Koljonen | Jun 23, 2008 at 03:17 AM
If you want the 50% line so much, and also miss the "Others", it's probably time to give up on the two-sided bar graph altogether, and go back to the 100% stacked bar graph. That's my usual default for three series that add up to 100%, of which two far outweigh the third.
Posted by: derek | Jun 23, 2008 at 12:13 PM
Great comments all! Derek's version is a nice alternative. There really is no need for any colors at all; I just need to put Obama and Clinton on the axis.
Posted by: Kaiser | Jun 23, 2008 at 07:44 PM
What might be a nice bit of extra value would be if we knew the numbers of voters in the cities, suburbs, and rures in WI and TN. Making the bar graphs into matrix graphs would add information about the urbanization of the two states, and the areas of the bars would sum to tell you who won the overall primary (at the moment you can't see who won in Tennessee because that's lost in the breakdown).
Posted by: derek | Jun 24, 2008 at 01:58 AM
I've made some small changes and additions in a follow-up:
http://peltiertech.com/WordPress/2008/06/24/close-races-2/
Posted by: Jon Peltier | Jun 24, 2008 at 03:29 PM
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Posted by: luke54 | Jun 25, 2008 at 01:03 AM