A pie chart displays categorical data as segments of a pie. It's a very common type of visualization, and it is often used in infographics in the media. However, I am not a huge fan of pie charts. They are poor for visualizing large numbers of categories, as the eye cannot differentiate between the different sizes of the segments:
- Good for visualizing: Not much, really! Pie charts are best restricted to dashboards, where you need a proportional view at a glance. However, if you must use a pie chart, make sure it is only for small numbers of categories.
- Don't use for: Visualizing more than, let's say, four categories, or for representing proportions accurately.
- Pros: Reasonably good at representing proportional data for a small number of categories. Bar charts generally do a better, more accurate job of this.
- Cons: Really bad for representing large numbers...