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 |