2.11. Pie Charts & Donuts
Why Pie Charts Are Not Ideal
Pie charts are often discouraged in data visualization. They can be difficult to read and interpret, as our brains struggle to compare angles and curved lines. Determining which slice is larger or smaller can be a challenge without hovering over the data points.
Best Practices for Pie Charts
If you must use pie charts, follow these guidelines to make them more bearable:
- Limit the number of categories: Use pie charts only when you have a few categories. The fewer slices, the easier it is to read and interpret the chart.
- Display actual numbers: Including the data values or percentages on the chart can make it easier for your audience to understand the information.
- Stick to two or three values: Pie charts are more effective when you have a limited number of categories, such as male vs. female or new vs. returning visitors.
Donut charts are a variation of pie charts, with a hollow center. The same rules apply—avoid using them if possible, and use them only for a few categories when necessary. Including the actual numbers can make them more readable.
Pie Chart Alternatives
One alternative to pie charts is the vertical bar chart, which displays the same data but with straight bars that are easier to compare. Color-coding the bars can help distinguish categories at a glance.
Another option is the single horizontal stacked bar chart, which shows distribution on a straight line instead of a curved one. This format is more space-efficient and easier to read than a traditional pie chart.
While pie charts can sometimes be useful for visualizing limited categories, they are generally less effective than other chart types like vertical bar charts and horizontal stacked bar charts. Always consider the most appropriate visualization type for your data to ensure clear and effective communication.