D3 Visualization

--- name: d3js-visualization description: "Professional data visualization creation using D3.js with support for interactive charts, custom visualizations, animations, and responsive design. Use for: (1) Creating custom interactive charts, (2) Building dashboards, (3) Network/graph visualizations, (4) Geographic data mapping, (5) Time series analysis, (6) Real-time data visualization, (7) Complex multi-dimensional data displays" --- # D3.js Data Visualization Skill ## What is D3.js D3.js (Data-Driven Documents) is a JavaScript library for producing dynamic, interactive data visualizations in web browsers. It uses HTML, SVG, and CSS standards to bind data to the DOM and apply data-driven transformations. ### When to Use D3.js **Choose D3.js when you need:** - Custom, unique visualizations not available in chart libraries - Fine-grained control over every visual element - Complex interactions and animations - Data-driven DOM manipulation beyond just charts - Performance with large datasets (when using Canvas) - Web standards-based visualizations **Consider alternatives when:** - Simple standard charts are sufficient (use Chart.js, Plotly) - Quick prototyping is priority (use Observable, Vega-Lite) - Static charts for print/reports (use matplotlib, ggplot2) - 3D visualizations (use Three.js, WebGL libraries) ### D3.js vs Other Libraries | Library | Best For | Learning Curve | Customization | |---------|----------|----------------|---------------| | D3.js | Custom visualizations | Steep | Complete | | Chart.js | Standard charts | Easy | Limited | | Plotly | Scientific plots | Medium | Good | | Highcharts | Business dashboards | Easy | Good | | Three.js | 3D graphics | Steep | Complete | --- ## Core Workflow ### 1. Project Setup **Option 1: CDN (Quick Start)** ```html D3 Visualization

``` **Option 2: NPM (Production)** ```bash npm install d3 ``` ```javascript // Import all of D3 import * as d3 from "d3"; // Or import specific modules import { select, selectAll } from "d3-selection"; import { scaleLinear, scaleTime } from "d3-scale"; ``` ### 2. Create Basic Chart ```javascript // Set up dimensions and margins const margin = {top: 20, right: 30, bottom: 40, left: 50}; const width = 800 - margin.left - margin.right; const height = 400 - margin.top - margin.bottom; // Create SVG const svg = d3.select("#chart") .append("svg") .attr("width", width + margin.left + margin.right) .attr("height", height + margin.top + margin.bottom) .append("g") .attr("transform", `translate(${margin.left},${margin.top})`); // Load and process data d3.csv("data.csv", d => ({ date: new Date(d.date), value: +d.value })).then(data => { // Create scales const xScale = d3.scaleTime() .domain(d3.extent(data, d => d.date)) .range([0, width]); const yScale = d3.scaleLinear() .domain([0, d3.max(data, d => d.value)]) .nice() .range([height, 0]); // Create and append axes svg.append("g") .attr("transform", `translate(0,${height})`) .call(d3.axisBottom(xScale)); svg.append("g") .call(d3.axisLeft(yScale)); // Create line generator const line = d3.line() .x(d => xScale(d.date)) .y(d => yScale(d.value)) .curve(d3.curveMonotoneX); // Draw line svg.append("path") .datum(data) .attr("d", line) .attr("fill", "none") .attr("stroke", "steelblue") .attr("stroke-width", 2); }); ``` ### 3. Add Interactivity **Tooltips:** ```javascript const tooltip = d3.select("body") .append("div") .attr("class", "tooltip") .style("position", "absolute") .style("visibility", "hidden") .style("background", "white") .style("border", "1px solid #ddd") .style("padding", "10px") .style("border-radius", "4px"); circles .on("mouseover", function(event, d) { tooltip .style("visibility", "visible") .html(`${d.name}
Value: ${d.value}`); }) .on("mousemove", function(event) { tooltip .style("top", (event.pageY - 10) + "px") .style("left", (event.pageX + 10) + "px"); }) .on("mouseout", function() { tooltip.style("visibility", "hidden"); }); ``` **Transitions:** ```javascript circles .transition() .duration(300) .ease(d3.easeCubicOut) .attr("r", 8); ``` ### 4. Implement Responsive Design ```javascript function createChart() { const container = d3.select("#chart"); const containerWidth = container.node().getBoundingClientRect().width; const margin = {top: 20, right: 30, bottom: 40, left: 50}; const width = containerWidth - margin.left - margin.right; const height = Math.min(width * 0.6, 500); container.selectAll("*").remove(); // Clear previous // Create SVG... } // Initial render createChart(); // Re-render on resize with debouncing let resizeTimer; window.addEventListener("resize", () => { clearTimeout(resizeTimer); resizeTimer = setTimeout(createChart, 250); }); ``` --- ## Key Principles ### Data Binding - Use `.data()` to bind data to DOM elements - Handle enter, update, and exit selections - Use key functions for consistent element-to-data matching - Modern syntax: use `.join()` for cleaner code ### Scales - Map data values (domain) to visual values (range) - Use appropriate scale types (linear, time, band, ordinal) - Apply `.nice()` to scales for rounded axis values - Invert y-scale range for bottom-up coordinates: `[height, 0]` ### SVG Coordinate System - Origin (0,0) is at top-left corner - Y increases downward (opposite of Cartesian) - Use margin convention for proper spacing - Group related elements with `` tags ### Performance - Use SVG for <1,000 elements - Use Canvas for >1,000 elements - Aggregate or sample large datasets - Debounce resize handlers --- ## Chart Selection Guide **Time series data?** → Line chart or area chart **Comparing categories?** → Bar chart (vertical or horizontal) **Showing relationships?** → Scatter plot or bubble chart **Part-to-whole?** → Donut chart or stacked bar (limit to 5-7 categories) **Network data?** → Force-directed graph **Distribution?** → Histogram or box plot See [`references/chart-types.md`](./references/chart-types.md) for detailed chart selection criteria and best practices. --- ## Common Patterns ### Quick Data Loading ```javascript // Load CSV with type conversion d3.csv("data.csv", d => ({ date: new Date(d.date), value: +d.value, category: d.category })).then(data => { createChart(data); }); ``` ### Quick Tooltip ```javascript selection .on("mouseover", (event, d) => { tooltip.style("visibility", "visible").html(`Value: ${d.value}`); }) .on("mousemove", (event) => { tooltip.style("top", event.pageY + "px").style("left", event.pageX + "px"); }) .on("mouseout", () => tooltip.style("visibility", "hidden")); ``` ### Quick Responsive SVG ```javascript svg .attr("viewBox", `0 0 ${width} ${height}`) .attr("preserveAspectRatio", "xMidYMid meet") .style("width", "100%") .style("height", "auto"); ``` --- ## Quality Standards ### Visual Quality - Use appropriate chart type for data - Apply consistent color schemes - Include clear axis labels and legends - Provide proper spacing with margin convention - Use appropriate scale types and ranges ### Interaction Quality - Add meaningful tooltips - Use smooth transitions (300-500ms duration) - Provide hover feedback - Enable keyboard navigation for accessibility - Implement zoom/pan for detailed exploration ### Code Quality - Use key functions in data joins - Handle enter, update, and exit properly - Clean up previous renders before updates - Use reusable chart pattern for modularity - Debounce expensive operations ### Accessibility - Add ARIA labels and descriptions - Provide keyboard navigation - Use colorblind-safe palettes - Include text alternatives for screen readers - Ensure sufficient color contrast --- ## Helper Resources ### Available Scripts - **data-helpers.js**: Data loading, parsing, and transformation utilities - **chart-templates.js**: Reusable chart templates for common visualizations See [`scripts/`](./scripts/) directory for implementations. ### Working Examples - **line-chart.html**: Time series visualization with tooltips - **bar-chart.html**: Grouped and stacked bar charts - **network-graph.html**: Force-directed network visualization See [`examples/`](./examples/) directory for complete implementations. ### Detailed References - **D3 Fundamentals**: SVG basics, data binding, selections, transitions, events → [`references/d3-fundamentals.md`](./references/d3-fundamentals.md) - **Scales and Axes**: All scale types, axis customization, color palettes → [`references/scales-and-axes.md`](./references/scales-and-axes.md) - **Paths and Shapes**: Line/area generators, arcs, force simulations → [`references/paths-and-shapes.md`](./references/paths-and-shapes.md) - **Data Transformation**: Loading, parsing, grouping, aggregation, date handling → [`references/data-transformation.md`](./references/data-transformation.md) - **Chart Types**: Detailed guidance on when to use each chart type → [`references/chart-types.md`](./references/chart-types.md) - **Advanced Patterns**: Reusable charts, performance optimization, responsive design → [`references/advanced-patterns.md`](./references/advanced-patterns.md) - **Common Pitfalls**: Frequent mistakes and their solutions → [`references/common-pitfalls.md`](./references/common-pitfalls.md) - **Integration Patterns**: Using D3 with React, Vue, Angular, Svelte → [`references/integration-patterns.md`](./references/integration-patterns.md) --- ## Troubleshooting **Chart not appearing?** - Check browser console for errors - Verify data loaded correctly - Ensure SVG has width and height - Check scale domains and ranges **Elements in wrong position?** - Verify scale domain matches data range - Check if y-scale range is inverted: `[height, 0]` - Confirm margin transform applied to `` element - Check SVG coordinate system (top-left origin) **Transitions not working?** - Ensure duration is reasonable (300-500ms) - Check if transition applied to selection, not data - Verify easing function is valid - Confirm elements exist before transitioning **Poor performance?** - Reduce number of DOM elements (use Canvas if >1,000) - Aggregate or sample data - Debounce resize handlers - Minimize redraws --- ## External Resources ### Official Documentation - D3.js API Reference: https://d3js.org/ - Observable Examples: https://observablehq.com/@d3 ### Learning Resources - "Interactive Data Visualization for the Web" by Scott Murray - D3 Graph Gallery: https://d3-graph-gallery.com/ - Amelia Wattenberger's D3 Tutorial: https://wattenberger.com/blog/d3 ### Color Tools - ColorBrewer: https://colorbrewer2.org/ - D3 Color Schemes: https://d3js.org/d3-scale-chromatic ### Inspiration - Observable Trending: https://observablehq.com/trending - Reddit r/dataisbeautiful: https://reddit.com/r/dataisbeautiful --- This skill provides comprehensive coverage of D3.js for creating professional, interactive data visualizations. Use the core workflow as a starting point, refer to the detailed references for specific topics, and customize the examples for your needs.

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