claude-d3js-skill

D3.js Visualisation

Overview

This skill provides guidance for creating sophisticated, interactive data visualisations using d3.js. D3.js (Data-Driven Documents) excels at binding data to DOM elements and applying data-driven transformations to create custom, publication-quality visualisations with precise control over every visual element. The techniques work across any JavaScript environment, including vanilla JavaScript, React, Vue, Svelte, and other frameworks.

When to use d3.js

Use d3.js for:

• Custom visualisations requiring unique visual encodings or layouts
• Interactive explorations with complex pan, zoom, or brush behaviours
• Network/graph visualisations (force-directed layouts, tree diagrams, hierarchies, chord diagrams)
• Geographic visualisations with custom projections
• Visualisations requiring smooth, choreographed transitions
• Publication-quality graphics with fine-grained styling control
• Novel chart types not available in standard libraries

Consider alternatives for:

• 3D visualisations - use Three.js instead

Core workflow

1. Set up d3.js

Import d3 at the top of your script:

import * as d3 from 'd3';

Or use the CDN version (7.x):

<script src="https://d3js.org/d3.v7.min.js"></script>

All modules (scales, axes, shapes, transitions, etc.) are accessible through the d3 namespace.

2. Choose the integration pattern

Pattern A: Direct DOM manipulation (recommended for most cases) Use d3 to select DOM elements and manipulate them imperatively. This works in any JavaScript environment:

function drawChart(data) {
  if (!data || data.length === 0) return;
 
  const svg = d3.select('#chart'); // Select by ID, class, or DOM element
 
  // Clear previous content
  svg.selectAll("*").

Pattern B: Declarative rendering (for frameworks with templating) Use d3 for data calculations (scales, layouts) but render elements via your framework:

function getChartElements(data) {
  const xScale = d3.scaleLinear()
    .domain([0, d3.max(data, d => d.value)])
    .range([0, 400]);
 
  return data.map((d

Use Pattern A for complex visualisations with transitions, interactions, or when leveraging d3's full capabilities. Use Pattern B for simpler visualisations or when your framework prefers declarative rendering.

3. Structure the visualisation code

Follow this standard structure in your drawing function:

function drawVisualization(data) {
  if (!data || data.length === 0) return;
 
  const svg =

4. Implement responsive sizing

Make visualisations responsive to container size:

function setupResponsiveChart(containerId, data) {
  const container = document.getElementById(containerId);
  const svg = d3.select(`#${containerId}`).append('svg');
 
  function

Or use ResizeObserver for more direct container monitoring:

function setupResponsiveChartWithObserver(svgElement, data) {
  const observer = new ResizeObserver(() => {
    const { width, height } = svgElement.getBoundingClientRect();
    d3.select(svgElement)
      .attr('width', width)

Common visualisation patterns

Bar chart

function drawBarChart(data, svgElement) {
  if (!data || data.length === 0) return;
 
  const svg = d3.

Line chart

const line = d3.line()
  .x(d => xScale(d.date))
  .y(d => yScale(d.value))
  .curve(d3.curveMonotoneX); // Smooth curve
 
g.append("path")
  .datum(data)
  .attr(

Scatter plot

g.selectAll("circle")
  .data(data)
  .join("circle")
  .attr("cx", d => xScale(d.x))
  .attr("cy", d => yScale(d.y))
  .attr("r", 

Chord diagram

A chord diagram shows relationships between entities in a circular layout, with ribbons representing flows between them:

function drawChordDiagram(data) {
  // data format: array of objects with source, target, and value

Heatmap

A heatmap uses colour to encode values in a two-dimensional grid, useful for showing patterns across categories:

Pie chart

const pie = d3.pie()
  .value(d => d.value)
  .sort(null);
 
const arc = d3.arc()
  .innerRadius(0)
  .outerRadius(Math.min(width, height) 

Force-directed network

const simulation = d3.forceSimulation(nodes)
  .force("link", d3.forceLink(links).id(d => d.id).distance(100))
  .

Adding interactivity

Tooltips

// Create tooltip div (outside SVG)
const tooltip = d3.select("body").append("div")
  .attr("class", "tooltip")
  .style("position", "absolute")

Zoom and pan

const zoom = d3.zoom()
  .scaleExtent([0.5, 10])
  .on("zoom", (event) => {
    g.attr("transform", event.transform);
  });
 
svg.call(zoom);

Click interactions

circles
  .on("click", function(event, d) {
    // Handle click (dispatch event, update app state, etc.)
    console.log("Clicked:", d);
 
    // Visual feedback
    d3.selectAll("circle").attr("fill", "steelblue");
    d3.select

Transitions and animations

Add smooth transitions to visual changes:

// Basic transition
circles
  .transition()
  .duration(750)
  .attr("r", 10);
 
// Chained transitions
circles
  .transition()
  .duration(500)
  .attr("fill"

Scales reference

Quantitative scales

// Linear scale
const xScale = d3.scaleLinear()
  .domain([0, 100])
  .range([0, 500]);
 
// Log scale (for exponential data)
const logScale = d3.scaleLog()
  .domain([1, 

Ordinal scales

// Band scale (for bar charts)
const bandScale = d3.scaleBand()
  .domain(['A', 'B', 'C', 'D'])
  .range([0, 400])
  .padding(0.1);
 
// Point scale (for line/scatter categories)
const pointScale

Sequential scales

// Sequential colour scale
const colourScale = d3.scaleSequential(d3.interpolateBlues)
  .domain([0, 100]);
 
// Diverging colour scale
const divScale = d3.scaleDiverging(d3.interpolateRdBu)
  .domain([-10, 0, 10]);

Best practices

Data preparation

Always validate and prepare data before visualisation:

// Filter invalid values
const cleanData = data.filter(d => d.value != null && !isNaN(d.value));
 
// Sort data if order matters
const sortedData = [...data].sort((a, b) => b.value - a.value);
 
// Parse dates

Performance optimisation

For large datasets (>1000 elements):

// Use canvas instead of SVG for many elements
// Use quadtree for collision detection
// Simplify paths with d3.line().curve(d3.curveStep)
// Implement virtual scrolling for large lists
// Use requestAnimationFrame for custom animations

Accessibility

Make visualisations accessible:

// Add ARIA labels
svg.attr("role", "img")
   .attr("aria-label", "Bar chart showing quarterly revenue");
 
// Add title and description
svg.append("title").text("Quarterly Revenue 2024");
svg.append("desc").text("Bar chart showing revenue growth across four quarters"

Styling

Use consistent, professional styling:

// Define colour palettes upfront
const colours = {
  primary: '#4A90E2',
  secondary: '#7B68EE',
  background: '#F5F7FA',
  text: '#333333',
  gridLines: '#E0E0E0'
};
 
// Apply consistent typography
svg.selectAll("text")
  .style("font-family"

Common issues and solutions

Issue: Axes not appearing

• Ensure scales have valid domains (check for NaN values)
• Verify axis is appended to correct group
• Check transform translations are correct

Issue: Transitions not working

• Call .transition() before attribute changes
• Ensure elements have unique keys for proper data binding
• Check that useEffect dependencies include all changing data

Issue: Responsive sizing not working

• Use ResizeObserver or window resize listener
• Update dimensions in state to trigger re-render
• Ensure SVG has width/height attributes or viewBox

Issue: Performance problems

• Limit number of DOM elements (consider canvas for >1000 items)
• Debounce resize handlers
• Use .join() instead of separate enter/update/exit selections
• Avoid unnecessary re-renders by checking dependencies

Resources

references/

Contains detailed reference materials:

• d3-patterns.md - Comprehensive collection of visualisation patterns and code examples
• scale-reference.md - Complete guide to d3 scales with examples
• colour-schemes.md - D3 colour schemes and palette recommendations

assets/

Contains boilerplate templates:

• chart-template.js - Starter template for basic chart
• interactive-template.js - Template with tooltips, zoom, and interactions
• sample-data.json - Example datasets for testing

These templates work with vanilla JavaScript, React, Vue, Svelte, or any other JavaScript environment. Adapt them as needed for your specific framework.

To use these resources, read the relevant files when detailed guidance is needed for specific visualisation types or patterns.