Data Visualizer

Build charts, dashboards, and interactive data visualizations using modern libraries. Covers Recharts (React), Chart.js (framework-agnostic), and D3.js (custom/advanced).

Library Selection

Library	Best For	React	Custom	Bundle (gzip)
Recharts	Quick React charts, standard types	Native	Limited	~139KB
Chart.js	Framework-agnostic, simple API	Wrapper	Moderate	~68KB (tree-shakeable)
D3.js	Custom visualizations, full control	Manual	Full	~13-30KB per module

Chart Type Selection

Chart	Best For	Avoid When
Line	Trends over time, continuous data	Categorical data
Bar	Comparing categories, rankings	Continuous data
Pie/Donut	Part-to-whole (max 5-7 slices)	>7 categories, precise comparison
Area	Volume over time, stacked categories	Too many overlapping series
Scatter	Correlation, outliers, distribution	Time series
Heatmap	Intensity across two dimensions	Simple comparisons

Dashboard Patterns

Pattern	Use Case	Key Feature
KPI Dashboard	Executive metrics	Trend indicators, card grid
Real-Time	Live monitoring	SSE/WebSocket, animation disabled
Interactive Filters	Exploratory analysis	Period/region selects, drill-down
Drill-Down	Hierarchical data	Click to zoom (year → month → day)

Responsive Design

Approach	Implementation
Container-based sizing	<ResponsiveContainer width="100%" height={300}>
Aspect ratio mode	<ResponsiveContainer width="100%" aspect={2}>
Mobile-aware	Reduce strokeWidth, height on small screens
Label simplification	Fewer axis labels on mobile

Common Mistakes

Mistake	Fix
Fixed width/height	Use ResponsiveContainer
Animation on real-time data	Set isAnimationActive={false}
Too many pie slices	Max 5-7 slices, group rest as "Other"
Non-accessible colors	Use WCAG AA compliant, colorblind-safe palette
Loading entire chart library	Lazy load with dynamic imports
No data formatting	Use Intl.NumberFormat for currency/percent

Delegation

• Explore data shape and available fields before choosing chart type: Use Explore agent
• Build a complete multi-chart dashboard from requirements: Use Task agent
• Plan visualization architecture for large-scale analytics pages: Use Plan agent

References

• Library Selection — Recharts, Chart.js, D3.js setup and examples
• Chart Types — line, bar, pie, area, scatter, heatmap with use cases
• Dashboard Patterns — KPI, real-time SSE, interactive filters, drill-down
• Design and Accessibility — color schemes, colorblind-safe palettes, responsive, animation
• Data Formatting and Export — number formatters, CSV export, PNG export
• Performance — lazy loading, virtualization for large datasets
• Storytelling and Annotation — data narratives, annotations, color strategy, edge states