March 21, 2013

An Example Where Circles are Useful in Graphs

The originally post by Naomi Robbins,:

I recently saw the infographic in Figure 1 and thought to myself, “Another application of bubbles in infographics.” After all, I criticized circles and bubbles in Misleading Graphs: Figures Not Drawn to Scale. In The Functional Art, Alberto Cairo wrote “No fashion plague is more prevalent as I write this book than the bubble.” I didn’t study Figure 1 carefully since the text is in Italian, a language that I don’t read.

This figure was originally published on July 22, 2012 in La Lettura, the Sunday cultural supplement of Corriere della Sera, the highest circulation newspaper of Italy. It was produced by Accurat, a design agency in Milan and New York that does amazing work.

Later I discovered Figure 1 was translated into English and discussed in Parson’s Journal for Information Mapping. There I learned that the circles represent the distance you can travel underground from the center of cities using their subway systems. Overlapping symbols show that you can get from one city to the other underground. I can’t think of a better way to show distances from the center of a city than with a circle.

The visualization then provides lots of other information by which each city’s subway system could be compared. Pictograms show the number of passengers, the stroke width of the circles shows the cost of a one-way ticket, and the little colored squares show the colors of the lines.

There is more than one takeaway from this story. First, our first impressions are not always correct. Second, exceptions exist for many graphical principles. There are examples where circles are an excellent choice to show the data we want to display.