While on holiday, I picked up this interesting chart on the Argentine paper Clarin, showing the results of a (daily) on-line poll. This presentation of percentages as a dot matrix of 100 points is the same concept that I described before as a "decile plot". Not sure why but at clarin.com, a different graphic (the bar chart) was used to present the same data. The bar chart is perhaps most visually appealing but the dot matrix allows readers to read off actual percentages by counting off the dots.
For comparison, look at the pie and donut charts that many publications would no doubt choke us with if they get their hands on this data.
I have already voiced my distaste for pies and donuts, here and here. OK, so they tell us the percentages add up to 100 and the bar chart doesn't. But how important is that factoid? So I still say: never use pies or donuts.
The dot matrix/decile plot has some potential but I'm not sure if it is better than the bar chart. Here is one possible rendition:
- I would rather not tip the square. (I also dislike the color scheme but have not altered it.)
- Since I don't care to tell readers they add to 100%, I stacked the groups one over the other so that it is much easier to eyeball the exact percentages. Because of this, I can omit printing the percentages. Of course, now the onus is on the graphic designer to make sure there are 100 dots, no more no less
- To reconcile form and function, I left off the decimal point. When you plot 100 dots, you have made the decision that each 1% is important so why would you then print 47.6% rather than 48%?
The irony is that for one data series, just printing the table is as good as anything.