VOL. III · CH. 3.13 · COMPONENT
Charts & Graphs
Turning numbers into a shape the eye can compare faster than a table of digits.
1 min read · 151 words
3.13.1Definition & Chart-Type Fit
A chart visually encodes data to reveal pattern, trend, or comparison. Fit matters more than style: line charts for trend over time, bar charts for comparing discrete categories, pie/donut charts only for simple part-to-whole with few segments.
3.13.2Common Mistakes
- Using a pie chart for more than 5–6 segments, where proportion becomes impossible to judge visually.
- Truncated or non-zero-based axes that visually exaggerate small differences.
- No accessible data table alternative for screen reader users.
3.13.3Best Practices
- Match chart type to the actual comparison being made, not to visual preference.
- Start value axes at zero unless there's a clearly labeled, deliberate reason not to.
- Provide an accessible data-table fallback alongside any critical visualization.
ExampleFinancial dashboards default to line charts for time-series metrics (revenue over months) specifically because trend direction is the question being asked, which line charts answer far faster than a table of numbers.