Celebrating Pi Day with Pie Charts (and other circular data visualizations)

Happy Pi Day! I hope everyone looking to celebrate today eats a yummy piece of pie or at least momentarily contemplates the remarkable mystery of the number pi. As a quick reminder, pi is the number found when any circle’s circumference is divided by its diameter (3.1415926535…). One of the most significant and mind-boggling facts about this number is that nobody actually knows its exact value because it is infinite, and the digits go on forever with no discernible pattern. This extraordinary number has a long history, and has helped us better understand our universe. It is even found in nature.

Circles are everywhere, including the world of data visualization. Using the Public Library Annual Report (PLAR) data let’s celebrate Pi Day by checking out some circular data visualizations. Of course, the logical place to start is pie charts! Pie charts have become controversial in the data world because of their overuse in situations they are not suited for. The last thing I want to do is lead libraries towards a visualization method that may not be the right fit for their data, but pie charts are tempting to use and easy to create, so it’s valuable to understand their place in data visualization and when not to use them…

Continue reading this post on LRS.org and check out more posts on research in a library context from Library Research Service.


LRS’s Colorado Public Library Data Users Group (DUG) mailing list provides instructions on data analysis and visualization, LRS news, and PLAR updates. To receive posts via email, please complete this form.