Choosing the Right Chart

Decision framework for selecting the most effective visualization for your data and message.

Quick Decision Tree

What are you showing?
│
├── COMPARISON between groups
│   ├── Few categories (2-5) → Bar chart (vertical)
│   ├── Many categories (6+) → Bar chart (horizontal)
│   ├── Over time → Line chart (grouped)
│   └── Part of whole → Stacked bar or pie (only if 2-5 segments)
│
├── DISTRIBUTION of values
│   ├── Single variable → Histogram + KDE
│   ├── Compare distributions → Box plot or violin plot
│   ├── Exact percentiles matter → Box plot
│   └── Shape matters → Violin plot or ridgeline
│
├── RELATIONSHIP between variables
│   ├── Two numeric → Scatter plot + regression line
│   ├── Numeric vs categorical → Strip/swarm plot
│   ├── Many numeric pairs → Pair plot or correlation heatmap
│   └── Three variables → Scatter with color/size encoding
│
├── TREND over time
│   ├── One metric → Line chart
│   ├── Multiple metrics → Multi-line or small multiples
│   ├── Cumulative → Area chart
│   └── Seasonal patterns → Seasonal decomposition plot
│
└── COMPOSITION
    ├── At one point in time → Pie chart (≤5 segments) or treemap
    ├── Over time → Stacked area
    └── Hierarchical → Treemap or sunburst

Rules of Thumb

Common Anti-Patterns

1. Dual Y-axes — Almost always misleading. Use small multiples instead.

2. 3D charts — Never add depth for decoration. It distorts perception.

3. Pie charts with >5 segments — Humans can't accurately compare angles.

4. Truncated Y-axis without indication — Either start at 0 or clearly mark the break.

5. Rainbow color schemes — Use sequential (light→dark) for ordered data, categorical for groups.

Color Guidelines

• Sequential data (low→high): Use single-hue gradient (light blue → dark blue)
• Diverging data (negative↔positive): Use two-hue gradient (red ← white → blue)
• Categorical data: Use distinct hues with similar saturation
• Highlighting: Use gray for context, color for focal point
• Accessibility: Always check with colorblind simulation (use viridis for safe default)