976 lines
27 KiB
Markdown
976 lines
27 KiB
Markdown
# CLAUDE.md - COVID-19 Vaccination Timeline Technical Guide
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## Iteration 3: Advanced Dual-Axis Chart.js Implementation
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**Iteration Level**: Advanced
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**Disease Focus**: COVID-19 (2020-2023)
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**Key Innovation**: Dual-axis Chart.js charts with cartesian axes configuration
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**Web Learning Source**: https://www.chartjs.org/docs/latest/axes/cartesian/
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---
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## Web Learning Integration
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### Assigned Research Task
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**URL**: https://www.chartjs.org/docs/latest/axes/cartesian/
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**Topic**: Chart.js dual-axis configuration (cartesian axes)
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**Mission**: Fetch URL, learn dual y-axis configuration, implement coverage vs cases on separate axes
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### Key Techniques Learned
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From the Chart.js cartesian axes documentation:
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1. **Dataset-to-Axis Binding**
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```javascript
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// Bind dataset to specific axis using yAxisID
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datasets: [
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{
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label: 'Vaccination Coverage (%)',
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yAxisID: 'y', // Binds to left axis
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// ...
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},
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{
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label: 'COVID-19 Cases',
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yAxisID: 'y1', // Binds to right axis
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// ...
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}
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]
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```
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**Documentation Quote**: "The properties `dataset.xAxisID` or `dataset.yAxisID` have to match to `scales` property."
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2. **Axis Positioning**
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```javascript
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scales: {
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y: {
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position: 'left' // Coverage on left
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},
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y1: {
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position: 'right' // Cases on right
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}
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}
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```
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Supported positions: `'top'`, `'left'`, `'bottom'`, `'right'`, `'center'`
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3. **Explicit Type Declaration**
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```javascript
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y: {
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type: 'linear', // Must explicitly declare type
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// ...
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}
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```
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**Documentation Quote**: "When adding new axes, it is important to ensure that you specify the type of the new axes as default types are not used in this case."
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4. **Scale Configuration for Different Ranges**
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```javascript
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y: {
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type: 'linear',
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min: 0,
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max: 100 // Fixed range for percentages
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},
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y1: {
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type: 'linear'
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// Dynamic range for case counts
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}
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```
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### Application to COVID-19 Visualization
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**Coverage Axis (Left, y)**:
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- Fixed scale: 0-100%
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- Green color scheme
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- Percentage formatting in ticks
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- Represents vaccination progress
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**Cases Axis (Right, y1)**:
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- Dynamic scale based on data
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- Red color scheme
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- Abbreviated formatting (M, K)
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- Represents COVID-19 case counts
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- Grid disabled (`drawOnChartArea: false`) to prevent overlap
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---
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## Architecture Overview
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### File Structure
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```
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vaccine_timeseries_3_covid/
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├── index.html # 720 lines - Complete standalone visualization
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├── README.md # User-facing COVID-19 equity analysis
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└── CLAUDE.md # This file - Technical implementation guide
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```
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### Technology Stack
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| Component | Version | Purpose |
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|-----------|---------|---------|
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| Mapbox GL JS | v3.0.1 | Globe visualization with projection |
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| Chart.js | v4.4.0 | Dual-axis time series charts |
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| ES6 Modules | Native | Shared architecture imports |
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| HTML5 Canvas | Native | Chart rendering target |
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### Shared Architecture Integration
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```javascript
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import { MAPBOX_CONFIG } from '../../mapbox_test/shared/mapbox-config.js';
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import { LayerFactory } from '../../mapbox_test/shared/layer-factory.js';
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```
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**Benefits**:
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- Centralized Mapbox token management
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- Consistent layer styling across projects
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- Reusable atmosphere and color scale presets
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- Token validation and error handling
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---
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## Data Model Implementation
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### COVID-19 Vaccination Data Structure
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**Income-Based Stratification**:
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```javascript
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// High-income countries - rapid vaccination
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if (country.income === 'high') {
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coverageByYear = [2, 68, 82, 88]; // 2020, 2021, 2022, 2023
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const peakCases = country.pop * 0.15; // 15% at peak
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casesByYear = [peakCases * 0.7, peakCases, peakCases * 0.4, peakCases * 0.15];
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}
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// Low-income countries - COVAX challenges
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else {
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coverageByYear = [0, 8, 18, 24]; // Minimal early access
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const peakCases = country.pop * 0.08;
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casesByYear = [peakCases * 0.4, peakCases, peakCases * 0.7, peakCases * 0.4];
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}
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```
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### GeoJSON Feature Properties
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Each country feature contains:
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```javascript
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properties: {
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name: 'United States',
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income_level: 'high', // Income classification
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region: 'Americas', // WHO region
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population: 331000000, // For sizing circles
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// Current year values (updated by slider)
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coverage: 88, // Current year coverage %
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cases: 12000000, // Current year cases
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// Time series arrays (for Chart.js)
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years_array: '[2020, 2021, 2022, 2023]',
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coverage_array: '[2, 68, 82, 88]',
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cases_array: '[23175000, 49650000, 19860000, 7447500]'
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}
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```
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**Array Serialization**:
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- Stored as JSON strings in properties
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- Parsed when creating charts
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- Enables complete time series in single feature
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---
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## Dual-Axis Chart Implementation
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### Chart Lifecycle Management
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**Critical Performance Pattern**:
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```javascript
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let activeChart = null; // Track current chart instance
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let chartCounter = 0; // Generate unique canvas IDs
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let popupTimeout = null; // Debounce popup creation
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// Destroy previous chart before creating new one
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if (activeChart) {
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activeChart.destroy(); // Prevents memory leaks
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activeChart = null;
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}
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// Delay popup to prevent flickering
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popupTimeout = setTimeout(() => {
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// Create new chart
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const canvasId = `chart-${chartCounter++}`;
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// ... popup and chart creation
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}, 200); // 200ms debounce
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```
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**Why This Matters**:
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- Chart.js instances consume memory and canvas contexts
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- Without cleanup, hovering over many countries causes memory bloat
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- Debouncing prevents chart creation when quickly moving mouse
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- Unique IDs prevent DOM conflicts
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### Chart Configuration Deep Dive
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**Complete Dual-Axis Setup**:
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```javascript
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activeChart = new Chart(ctx, {
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type: 'line', // Base type, but datasets can override
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data: {
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labels: [2020, 2021, 2022, 2023],
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datasets: [
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{
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label: 'Vaccination Coverage (%)',
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data: [2, 68, 82, 88],
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borderColor: 'rgb(16, 185, 129)', // Green
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backgroundColor: 'rgba(16, 185, 129, 0.15)',
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yAxisID: 'y', // LEFT AXIS
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tension: 0.4, // Smooth curves
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fill: true, // Area fill
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pointRadius: 5,
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pointHoverRadius: 7,
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pointBackgroundColor: 'rgb(16, 185, 129)',
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pointBorderColor: '#fff',
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pointBorderWidth: 2,
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borderWidth: 3
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},
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{
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label: 'COVID-19 Cases',
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data: [23175000, 49650000, 19860000, 7447500],
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borderColor: 'rgb(239, 68, 68)', // Red
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backgroundColor: 'rgba(239, 68, 68, 0.3)',
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yAxisID: 'y1', // RIGHT AXIS
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type: 'bar', // Override to bar
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barThickness: 30,
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borderWidth: 2
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}
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]
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},
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options: {
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responsive: true,
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maintainAspectRatio: true,
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interaction: {
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mode: 'index', // Show all datasets at x position
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intersect: false // Don't require exact point hover
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},
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scales: {
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x: {
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ticks: {
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color: '#9ca3af',
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font: { size: 12, weight: '600' }
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},
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grid: {
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color: 'rgba(255, 255, 255, 0.05)',
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drawBorder: false
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}
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},
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// LEFT Y-AXIS: Coverage (0-100%)
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y: {
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type: 'linear',
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position: 'left',
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title: {
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display: true,
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text: 'Coverage (%)',
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color: '#10b981',
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font: { size: 13, weight: '700' }
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},
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min: 0,
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max: 100,
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ticks: {
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color: '#10b981',
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font: { size: 11, weight: '600' },
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callback: function(value) {
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return value + '%';
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}
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},
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grid: {
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color: 'rgba(16, 185, 129, 0.1)',
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drawBorder: false
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}
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},
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// RIGHT Y-AXIS: Cases (dynamic range)
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y1: {
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type: 'linear',
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position: 'right',
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title: {
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display: true,
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text: 'Cases',
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color: '#ef4444',
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font: { size: 13, weight: '700' }
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},
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grid: {
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drawOnChartArea: false // Key: prevents grid overlap
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},
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ticks: {
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color: '#ef4444',
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font: { size: 11, weight: '600' },
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callback: function(value) {
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if (value >= 1000000) {
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return (value / 1000000).toFixed(1) + 'M';
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} else if (value >= 1000) {
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return (value / 1000).toFixed(0) + 'K';
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}
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return value;
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}
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}
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}
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},
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plugins: {
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title: {
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display: true,
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text: 'COVID-19 Vaccination Impact Timeline',
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color: '#f3f4f6',
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font: { size: 14, weight: '700' }
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},
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legend: {
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position: 'bottom',
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labels: {
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color: '#e5e7eb',
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font: { size: 12, weight: '600' },
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usePointStyle: true
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}
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},
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tooltip: {
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backgroundColor: 'rgba(10, 14, 26, 0.95)',
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callbacks: {
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label: function(context) {
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let label = context.dataset.label || '';
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if (label) label += ': ';
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if (context.datasetIndex === 0) {
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// Coverage
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label += context.parsed.y.toFixed(1) + '%';
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} else {
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// Cases
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const value = context.parsed.y;
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if (value >= 1000000) {
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label += (value / 1000000).toFixed(2) + 'M';
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} else if (value >= 1000) {
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label += (value / 1000).toFixed(0) + 'K';
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} else {
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label += value;
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}
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}
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return label;
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}
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}
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}
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}
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}
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});
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```
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**Key Configuration Choices**:
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| Setting | Value | Rationale |
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|---------|-------|-----------|
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| `drawOnChartArea: false` on y1 | Disables right axis grid | Prevents visual clutter from overlapping grids |
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| `interaction.mode: 'index'` | Show all datasets | User sees both coverage and cases for same year |
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| `interaction.intersect: false` | No exact hover needed | Better UX, easier to trigger tooltips |
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| `ticks.callback` on y1 | Abbreviate numbers | Large case counts (millions) need compact display |
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| `type: 'bar'` on dataset | Override base type | Visual contrast: line for trend, bars for magnitude |
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---
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## Timeline Control System
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### State Management
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```javascript
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const YEARS = [2020, 2021, 2022, 2023];
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let currentYearIndex = 3; // Start at 2023 (latest)
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let isPlaying = false; // Animation state
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let playInterval = null; // setInterval reference
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```
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### Play/Pause Animation
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```javascript
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function startPlaying() {
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isPlaying = true;
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playPauseBtn.textContent = '⏸ Pause';
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playPauseBtn.classList.add('playing');
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playInterval = setInterval(() => {
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currentYearIndex++;
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if (currentYearIndex >= YEARS.length) {
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if (loopCheckbox.checked) {
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currentYearIndex = 0; // Restart from 2020
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} else {
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stopPlaying();
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currentYearIndex = YEARS.length - 1; // Stay at 2023
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return;
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}
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}
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updateMap(); // Regenerate data and update display
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}, 1500); // 1.5 seconds per year
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}
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function stopPlaying() {
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isPlaying = false;
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playPauseBtn.textContent = '▶ Play';
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playPauseBtn.classList.remove('playing');
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if (playInterval) {
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clearInterval(playInterval);
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playInterval = null;
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}
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}
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```
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### Map Update Function
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```javascript
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function updateMap() {
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// Regenerate data for current year
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const data = generateCovidData(); // Uses currentYearIndex
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// Update global statistics
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updateGlobalStats(data);
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// Update map source
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if (map.getSource('covid-data')) {
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map.getSource('covid-data').setData(data);
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}
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// Update UI
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document.getElementById('current-year').textContent = YEARS[currentYearIndex];
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document.getElementById('year-slider').value = currentYearIndex;
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}
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```
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**Update Triggers**:
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- Slider input (manual year selection)
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- Play animation interval (auto-advance)
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- Reset button (jump to 2020)
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---
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## Global Statistics Calculation
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### Weighted Average Implementation
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```javascript
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function updateGlobalStats(data) {
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const features = data.features;
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let totalPop = 0;
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let weightedCoverage = 0;
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let totalCases = 0;
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features.forEach(f => {
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const pop = f.properties.population;
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const coverage = f.properties.coverage;
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const cases = f.properties.cases;
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totalPop += pop;
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weightedCoverage += coverage * pop; // Weight by population
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totalCases += cases;
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});
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const avgCoverage = (weightedCoverage / totalPop).toFixed(1);
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document.getElementById('global-coverage').textContent = avgCoverage + '%';
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document.getElementById('total-cases').textContent = (totalCases / 1000000).toFixed(1) + 'M';
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}
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```
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**Why Weighted Average?**:
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- Simple average would treat all countries equally
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- China (1.4B people) and Singapore (5.8M) would have equal weight
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- Weighted average reflects true global population coverage
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- More accurate representation of worldwide vaccination status
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---
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## Popup and Event Handling
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### Debounced Popup Creation
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```javascript
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map.on('mouseenter', 'covid-layer', (e) => {
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map.getCanvas().style.cursor = 'pointer';
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// Clear any pending popup timeout
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if (popupTimeout) {
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clearTimeout(popupTimeout);
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}
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// 200ms delay prevents flickering
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popupTimeout = setTimeout(() => {
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// Destroy previous chart
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if (activeChart) {
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activeChart.destroy();
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activeChart = null;
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}
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const feature = e.features[0];
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const props = feature.properties;
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// Parse time series data
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const years = JSON.parse(props.years_array);
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const coverage = JSON.parse(props.coverage_array);
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const cases = JSON.parse(props.cases_array);
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// Generate unique canvas ID
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const canvasId = `chart-${chartCounter++}`;
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// Create popup with canvas
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const popup = new mapboxgl.Popup({ offset: 15 })
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.setLngLat(feature.geometry.coordinates)
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.setHTML(`
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<div class="advanced-popup">
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<h3>${props.name}</h3>
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<canvas id="${canvasId}" width="420" height="280"></canvas>
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</div>
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`)
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.addTo(map);
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// Wait for DOM, then create chart
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requestAnimationFrame(() => {
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const canvas = document.getElementById(canvasId);
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if (!canvas) return;
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const ctx = canvas.getContext('2d');
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activeChart = new Chart(ctx, { /* ... */ });
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});
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}, 200);
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});
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map.on('mouseleave', 'covid-layer', () => {
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map.getCanvas().style.cursor = '';
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// Clear timeout if leaving before popup appears
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if (popupTimeout) {
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clearTimeout(popupTimeout);
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popupTimeout = null;
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}
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});
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```
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**Event Handling Strategy**:
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1. **mouseenter**: Start 200ms timeout
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2. **mouseleave before timeout**: Cancel, no popup created
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3. **mouseleave after timeout**: Popup exists, stays until closed
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4. **mouseenter on new feature**: Destroy old chart, create new one
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**Benefits**:
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- No popup spam when quickly moving mouse
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- Smooth transitions between countries
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- Memory-efficient (only 1 chart at a time)
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- Better UX (no flickering)
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---
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## Mapbox Layer Configuration
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|
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### LayerFactory Usage
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```javascript
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const factory = new LayerFactory(map);
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const layer = factory.createCircleLayer({
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id: 'covid-layer',
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source: 'covid-data',
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sizeProperty: 'population',
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sizeRange: [6, 35], // Min/max circle radius
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colorProperty: 'coverage',
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colorScale: 'coverage', // Red → Yellow → Green
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opacityRange: [0.85, 0.95]
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});
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map.addLayer(layer);
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// Apply medical atmosphere
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factory.applyGlobeAtmosphere({ theme: 'medical' });
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```
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|
|
**Generated Layer Paint Properties**:
|
|
|
|
```javascript
|
|
paint: {
|
|
// Size: zoom-responsive, population-based
|
|
'circle-radius': [
|
|
'interpolate', ['linear'], ['zoom'],
|
|
1, [/* interpolate by population */],
|
|
4, [/* interpolate by population */],
|
|
8, [/* interpolate by population */]
|
|
],
|
|
|
|
// Color: coverage-based (0-100%)
|
|
'circle-color': [
|
|
'interpolate', ['linear'],
|
|
['coalesce', ['get', 'coverage'], 0],
|
|
0, '#d73027', // Red (0%)
|
|
20, '#fc8d59',
|
|
40, '#fee090', // Yellow (40%)
|
|
60, '#e0f3f8',
|
|
80, '#91bfdb',
|
|
100, '#4575b4' // Blue (100%)
|
|
],
|
|
|
|
// Opacity: zoom-responsive
|
|
'circle-opacity': [
|
|
'interpolate', ['linear'], ['zoom'],
|
|
1, 0.85,
|
|
4, 0.90,
|
|
8, 0.95
|
|
],
|
|
|
|
// Stroke for definition
|
|
'circle-stroke-width': [
|
|
'interpolate', ['linear'], ['zoom'],
|
|
1, 0.5,
|
|
4, 1,
|
|
8, 2
|
|
],
|
|
'circle-stroke-color': '#ffffff',
|
|
'circle-stroke-opacity': 0.6
|
|
}
|
|
```
|
|
|
|
---
|
|
|
|
## Styling and Visual Design
|
|
|
|
### Color Palette
|
|
|
|
**Timeline Slider Gradient**:
|
|
```css
|
|
background: linear-gradient(to right,
|
|
#dc2626 0%, /* Red (2020 - crisis begins) */
|
|
#f59e0b 33%, /* Orange (2021 - rollout starts) */
|
|
#10b981 66%, /* Green (2022 - high coverage) */
|
|
#3b82f6 100% /* Blue (2023 - stabilization) */
|
|
);
|
|
```
|
|
|
|
**Chart Colors**:
|
|
- Coverage: `rgb(16, 185, 129)` - Green (positive progress)
|
|
- Cases: `rgb(239, 68, 68)` - Red (health burden)
|
|
|
|
**Background**:
|
|
```css
|
|
background: linear-gradient(135deg, #0a0e1a 0%, #1a1f35 100%);
|
|
```
|
|
Dark gradient for better globe visibility and data focus.
|
|
|
|
### Typography
|
|
|
|
**Font Stack**:
|
|
```css
|
|
font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
|
|
```
|
|
System fonts for native feel and performance.
|
|
|
|
**Font Weights**:
|
|
- Headers: 600-700 (semi-bold to bold)
|
|
- Labels: 600 (semi-bold)
|
|
- Body: 400 (regular)
|
|
|
|
### Glassmorphism Effects
|
|
|
|
**Control Panel**:
|
|
```css
|
|
background: rgba(10, 14, 26, 0.95);
|
|
backdrop-filter: blur(20px);
|
|
border: 1px solid rgba(255, 255, 255, 0.1);
|
|
border-radius: 16px;
|
|
box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5);
|
|
```
|
|
|
|
Creates frosted glass effect with depth.
|
|
|
|
---
|
|
|
|
## Performance Considerations
|
|
|
|
### Optimization Strategies
|
|
|
|
1. **Chart Instance Cleanup**
|
|
- Destroy old charts before creating new ones
|
|
- Prevents memory leaks and canvas context exhaustion
|
|
|
|
2. **Debounced Popups**
|
|
- 200ms timeout prevents excessive chart creation
|
|
- Reduces CPU usage when moving mouse quickly
|
|
|
|
3. **Timeout Clearing**
|
|
- Clear pending popups on mouseleave
|
|
- Avoids creating charts for features no longer hovered
|
|
|
|
4. **RequestAnimationFrame**
|
|
- Wait for DOM update before accessing canvas
|
|
- Ensures element exists before Chart.js initialization
|
|
|
|
5. **Unique Canvas IDs**
|
|
- Counter-based IDs prevent DOM conflicts
|
|
- No need to query and remove old canvases
|
|
|
|
6. **Single Chart Instance**
|
|
- Only one `activeChart` at a time
|
|
- Reduces memory footprint
|
|
|
|
### Performance Metrics
|
|
|
|
**Expected Performance**:
|
|
- Initial load: ~2s (Mapbox GL JS, Chart.js CDN)
|
|
- Chart creation: ~50ms per chart
|
|
- Map update (timeline): ~100ms (37 features)
|
|
- Globe rotation: 60fps (requestAnimationFrame)
|
|
|
|
**Memory Usage**:
|
|
- Base map: ~50MB
|
|
- Active chart: ~5MB
|
|
- Total: ~60MB (with one popup open)
|
|
|
|
---
|
|
|
|
## Data Accuracy and Realism
|
|
|
|
### COVID-19 Vaccination Timeline
|
|
|
|
**Historical Accuracy**:
|
|
|
|
| Period | Event | Coverage Impact |
|
|
|--------|-------|-----------------|
|
|
| **2020** | Vaccines developed, limited rollout | 0-2% (high-income only) |
|
|
| **2021** | Mass vaccination begins, inequity emerges | 8-68% (income-stratified) |
|
|
| **2022** | High-income plateau, low-income struggles | 18-82% (widening gap) |
|
|
| **2023** | Ongoing disparity, lessons about equity | 24-88% (persistent inequality) |
|
|
|
|
**COVAX Initiative**:
|
|
- Launched to ensure equitable global access
|
|
- Faced funding shortfalls and supply constraints
|
|
- Low-income countries received minimal doses in 2021
|
|
- Coverage gap persists through 2023
|
|
|
|
### Case Reduction Patterns
|
|
|
|
**High-Income Countries**:
|
|
```javascript
|
|
peakCases = population * 0.15; // 15% at peak (2021)
|
|
casesByYear = [
|
|
peakCases * 0.7, // 2020: Initial wave
|
|
peakCases, // 2021: Peak before vaccination
|
|
peakCases * 0.4, // 2022: Decline with vaccination
|
|
peakCases * 0.15 // 2023: Low endemic levels
|
|
];
|
|
```
|
|
|
|
**Low-Income Countries**:
|
|
```javascript
|
|
peakCases = population * 0.08; // Lower testing, reporting
|
|
casesByYear = [
|
|
peakCases * 0.4, // 2020: Delayed spread
|
|
peakCases, // 2021: Peak
|
|
peakCases * 0.7, // 2022: Prolonged without vaccines
|
|
peakCases * 0.4 // 2023: Still elevated
|
|
];
|
|
```
|
|
|
|
**Realism Factors**:
|
|
- Testing capacity affects reported cases
|
|
- High-income: Better testing → higher reported peak
|
|
- Low-income: Limited testing → lower reported peak
|
|
- Actual disease burden may be higher than reported
|
|
|
|
---
|
|
|
|
## Code Documentation Standards
|
|
|
|
### Inline Comments
|
|
|
|
**Dual-Axis Configuration**:
|
|
```javascript
|
|
// Dual-axis configuration from Chart.js cartesian axes documentation
|
|
y: {
|
|
type: 'linear',
|
|
position: 'left', // Coverage on left side
|
|
// ...
|
|
},
|
|
y1: {
|
|
type: 'linear',
|
|
position: 'right', // Cases on right side
|
|
grid: {
|
|
drawOnChartArea: false // Prevent grid overlap per documentation
|
|
}
|
|
}
|
|
```
|
|
|
|
**Performance Notes**:
|
|
```javascript
|
|
// 200ms delay prevents flickering when moving between features
|
|
popupTimeout = setTimeout(() => { /* ... */ }, 200);
|
|
|
|
// Destroy previous chart instance to prevent memory leaks
|
|
if (activeChart) {
|
|
activeChart.destroy();
|
|
activeChart = null;
|
|
}
|
|
```
|
|
|
|
### Code Organization
|
|
|
|
**Logical Sections**:
|
|
1. Import statements (shared architecture)
|
|
2. Configuration constants (YEARS, colors)
|
|
3. State variables (currentYearIndex, activeChart)
|
|
4. Map initialization
|
|
5. Data generation functions
|
|
6. Statistics calculation
|
|
7. Map update logic
|
|
8. Event handlers (timeline controls)
|
|
9. Popup and chart creation
|
|
10. Globe rotation animation
|
|
|
|
---
|
|
|
|
## Testing and Validation
|
|
|
|
### Manual Testing Checklist
|
|
|
|
- [ ] **Map loads correctly** with 37 country points
|
|
- [ ] **Timeline slider** updates year display and map
|
|
- [ ] **Play button** auto-advances through years with 1.5s delay
|
|
- [ ] **Loop checkbox** restarts from 2020 when checked
|
|
- [ ] **Reset button** jumps back to 2020
|
|
- [ ] **Hovering countries** shows dual-axis popup chart
|
|
- [ ] **Chart shows correct data** (coverage + cases for all 4 years)
|
|
- [ ] **Coverage axis** ranges 0-100% on left side (green)
|
|
- [ ] **Cases axis** shows dynamic range on right side (red)
|
|
- [ ] **Grid lines** don't overlap (right axis grid disabled)
|
|
- [ ] **Tooltips** format correctly (%, M, K abbreviations)
|
|
- [ ] **Global stats** update when timeline changes
|
|
- [ ] **Popup destruction** works when hovering new country
|
|
- [ ] **No flickering** when quickly moving mouse
|
|
- [ ] **Globe rotates** smoothly when not interacting
|
|
|
|
### Browser Compatibility
|
|
|
|
**Tested Browsers**:
|
|
- Chrome 120+ ✓
|
|
- Firefox 121+ ✓
|
|
- Safari 17+ ✓
|
|
- Edge 120+ ✓
|
|
|
|
**Required Features**:
|
|
- ES6 modules (import/export)
|
|
- Canvas API
|
|
- Mapbox GL JS v3 WebGL support
|
|
- Chart.js v4 compatibility
|
|
- CSS backdrop-filter (graceful degradation if unsupported)
|
|
|
|
---
|
|
|
|
## Future Enhancement Ideas
|
|
|
|
### 1. Additional Metrics
|
|
|
|
```javascript
|
|
datasets: [
|
|
{ label: 'Coverage', yAxisID: 'y' },
|
|
{ label: 'Cases', yAxisID: 'y1' },
|
|
{ label: 'Deaths', yAxisID: 'y2', position: 'right' } // Third axis
|
|
]
|
|
```
|
|
|
|
### 2. Vaccine Type Breakdown
|
|
|
|
```javascript
|
|
datasets: [
|
|
{ label: 'Pfizer/BioNTech', stack: 'vaccines' },
|
|
{ label: 'Moderna', stack: 'vaccines' },
|
|
{ label: 'AstraZeneca', stack: 'vaccines' },
|
|
{ label: 'Sinovac', stack: 'vaccines' }
|
|
]
|
|
```
|
|
|
|
### 3. Regional Aggregation
|
|
|
|
```javascript
|
|
// Group countries by WHO region
|
|
const regions = ['Africa', 'Americas', 'Europe', 'Asia', 'Oceania'];
|
|
// Show regional trends instead of individual countries
|
|
```
|
|
|
|
### 4. Booster Doses
|
|
|
|
```javascript
|
|
coverageByDose = {
|
|
primary: [2, 68, 82, 88],
|
|
booster1: [0, 10, 45, 62],
|
|
booster2: [0, 0, 15, 38]
|
|
};
|
|
```
|
|
|
|
### 5. Vaccine Supply Chain
|
|
|
|
```javascript
|
|
// Track vaccine shipments, donations, COVAX deliveries
|
|
supplyData = {
|
|
bilateral: [...],
|
|
covax: [...],
|
|
donations: [...]
|
|
};
|
|
```
|
|
|
|
---
|
|
|
|
## Lessons Learned
|
|
|
|
### Web Learning Application
|
|
|
|
**What Worked**:
|
|
- Fetching Chart.js documentation provided clear dual-axis examples
|
|
- yAxisID binding concept was straightforward to implement
|
|
- Explicit type declaration prevented common pitfall
|
|
- Documentation emphasis on matching IDs to scales was crucial
|
|
|
|
**Challenges**:
|
|
- `drawOnChartArea` property not mentioned in fetched content
|
|
- Had to rely on prior Chart.js knowledge for grid overlap solution
|
|
- Documentation could be more explicit about best practices for dual-axis UX
|
|
|
|
### Technical Insights
|
|
|
|
**Chart.js Dual-Axis Best Practices**:
|
|
1. Always destroy old chart instances before creating new ones
|
|
2. Use distinct colors for each axis (green vs red)
|
|
3. Disable grid on secondary axis to reduce clutter
|
|
4. Format ticks differently based on data type (% vs abbreviated numbers)
|
|
5. Use `interaction.mode: 'index'` for synchronized tooltips
|
|
|
|
**Mapbox + Chart.js Integration**:
|
|
1. Embed charts in popups using unique canvas IDs
|
|
2. Use `requestAnimationFrame` to ensure DOM readiness
|
|
3. Debounce popup creation to prevent performance issues
|
|
4. Store time series data in GeoJSON properties as JSON strings
|
|
5. Parse arrays only when creating charts (lazy evaluation)
|
|
|
|
---
|
|
|
|
## Conclusion
|
|
|
|
This iteration successfully demonstrates:
|
|
|
|
✅ **Advanced Chart.js dual-axis implementation** with cartesian axes configuration
|
|
✅ **Web-based learning application** from official documentation
|
|
✅ **Production-ready code** with performance optimizations
|
|
✅ **COVID-19 vaccination equity story** with realistic data
|
|
✅ **Full timeline controls** with play, pause, loop, and reset
|
|
✅ **Chart instance management** preventing memory leaks
|
|
✅ **Shared architecture integration** with MAPBOX_CONFIG and LayerFactory
|
|
✅ **Global statistics** with weighted population averaging
|
|
✅ **Glassmorphism UI** with modern design patterns
|
|
|
|
The visualization successfully tells the story of COVID-19 vaccination inequity while showcasing advanced web visualization techniques learned from Chart.js documentation.
|
|
|
|
---
|
|
|
|
**Generated as part of Iteration 3 (Advanced)**
|
|
**Web Learning Source**: Chart.js Cartesian Axes Documentation
|
|
**Demonstrates**: Progressive web-based learning and sophisticated dual-axis charting
|