A grouped bar chart places multiple data series side by side within each category. It is also called a clustered bar chart. By arranging subgroups next to one another, it allows comparison both across categories and within each category.
Examples include population by gender across regions, or sales by department across years.
Historical Background
Grouped bar charts evolved from the basic bar chart, which William Playfair introduced in the eighteenth century. As comparative statistics expanded, placing multiple bars within a category became a natural way to compare series directly.
Data Structure
| Data | Role |
|---|---|
| Main category | Group on the axis |
| Series or subgroup | Bars within each group |
| Value | Bar length |
| Color | Identifies series |
Purpose
The purpose is to compare several series across shared categories. Unlike stacked bars, grouped bars make individual series values easier to compare because each bar has its own baseline.
Use Cases
- Sales by year and department
- Population by gender and region
- Survey scores by group
- Product metrics by market
Design Notes
- Limit the number of series per group.
- Use clear spacing between groups.
- Keep series order consistent.
- Consider direct labels when legends become burdensome.
- Use stacked bars if the total is more important than individual comparison.
Summary
Grouped bar charts are a reliable choice for comparing multiple series within common categories. They become difficult when too many subgroups are added, so restraint is important.