visualize-population-density | Goong Documents

Use a variable binding expression to calculate and display population density.
Visualize population density

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Visualize population density</title>
<meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no" />
<script src="https://cdn.jsdelivr.net/npm/@goongmaps/goong-js@1.0.9/dist/goong-js.js"></script>
<link href="https://cdn.jsdelivr.net/npm/@goongmaps/goong-js@1.0.9/dist/goong-js.css" rel="stylesheet" />
<style>
	body { margin: 0; padding: 0; }
    #map { position: absolute; top: 0; bottom: 0; width: 100%; }
</style>
</head>
<body>

<div id="map"></div>
<script>
    goongjs.accessToken = 'wnicbAmnNkoMHNYUKWnlFHezV189FjmMwkNJ7hKW';
    var map = new goongjs.Map({
        container: 'map', // container id
        style: 'https://tiles.goong.io/assets/goong_map_web.json', // stylesheet location
        center: [30.0222, -1.9596], // starting position [lng, lat]
        zoom: 7 // starting zoom
    });

    map.on('load', function () {
        map.addSource('rwanda-provinces', {
            'type': 'geojson',
            'data': 'https://docs.goong.io/assets/rwanda-provinces.geojson'
        });
        map.addLayer({
            'id': 'rwanda-provinces',
            'type': 'fill',
            'source': 'rwanda-provinces',
            'layout': {},
            'paint': {
                'fill-color': [
                    'let',
                    'density',
                    ['/', ['get', 'population'], ['get', 'sq-km']],
                    [
                        'interpolate',
                        ['linear'],
                        ['zoom'],
                        8,
                        [
                            'interpolate',
                            ['linear'],
                            ['var', 'density'],
                            274,
                            ['to-color', '#edf8e9'],
                            1551,
                            ['to-color', '#006d2c']
                        ],
                        10,
                        [
                            'interpolate',
                            ['linear'],
                            ['var', 'density'],
                            274,
                            ['to-color', '#eff3ff'],
                            1551,
                            ['to-color', '#08519c']
                        ]
                    ]
                ],
                'fill-opacity': 0.7
            }
        });
    });
</script>
</body>
</html>