26 Pie Charts. 2D and 3D
Pie charts show proportions and percentages among categories. Data is represented in a circular format, where each slice corresponds to a category and the size of the slice is proportional to its share of the total, for example, the share of a district’s cultivated area given to each crop.
26.1 2D Pie Chart
A 2D pie chart is a straightforward way to visualize proportional data, widely used in reports and presentations.
Advantages:
- Clarity and precision: segments are easily comparable, making relative slice sizes straightforward to interpret.
- Simplicity: without an added dimension, 2D charts are cleaner and keep attention on the data rather than the design.
- Accuracy: proportions read linearly, with no perspective distortion.
Limitations:
- 2D pie charts can feel visually plain next to more elaborate chart types, which matters in presentations where visual impact is the goal.
26.1.1 R Code
26.2 Donut Chart
A donut chart is a pie chart with the center removed. The hole gives it a lighter, more modern look, and can hold a summary label or total value in the middle.
26.3 Exploded Pie Chart
An exploded pie chart pulls one slice outward from the rest, usually the one the chart is meant to draw attention to, such as the district’s leading crop by area.
26.4 3D Pie Chart
A 3D pie chart adds a depth dimension to the traditional pie chart. It can look visually striking, but the added perspective distorts how slice sizes are perceived. A near-side slice reads as larger than an equally-sized far-side slice. Current data-visualization guidance generally discourages 3D pie charts even for marketing materials, for exactly this reason; a 2D pie chart (or a bar chart, which handles more than a handful of categories far better) is the safer default. It’s shown here for completeness, since it still turns up in some tools and older reports.
26.4.1 R Code
In base R, a true 3D pie chart isn’t built in, but the plotrix package provides one.
- For business, research, or extension reports where clarity and accurate comparison matter, a 2D pie chart (or a bar chart) is the better choice.
- Reserve a 3D pie chart, if at all, for a very small number of slices (two or three) in a purely decorative context. Never for a chart someone needs to read numbers off of.
Summary
| Concept | Description |
|---|---|
| Pie Charts. 2D and 3D | |
| 2D Pie Chart | Shows each category's proportional share of a whole using slice size; accurate and easy to compare |
| Donut Chart | A pie chart with the center removed, giving a lighter look and room for a central label |
| Exploded Pie Chart | Pulls one slice outward to draw attention to it, e.g., a district's leading crop |
| 3D Pie Chart | Adds visual depth but distorts perceived slice size; discouraged for analytical use, shown here for completeness |