Visualize population density
Use a variable binding expression to calculate and display population density.
<!DOCTYPE html>
<html lang="en">
<head>
<title>Visualize population density</title>
<meta property="og:description" content="Use a variable binding expression to calculate and display population density." />
<meta charset='utf-8'>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel='stylesheet' href='https://unpkg.com/maplibre-gl@4.7.1/dist/maplibre-gl.css' />
<script src='https://unpkg.com/maplibre-gl@4.7.1/dist/maplibre-gl.js'></script>
<style>
body { margin: 0; padding: 0; }
html, body, #map { height: 100%; }
</style>
</head>
<body>
<div id="map"></div>
<script>
const map = new maplibregl.Map({
container: 'map', // container id
style:
'https://api.maptiler.com/maps/streets/style.json?key=get_your_own_OpIi9ZULNHzrESv6T2vL', // stylesheet location
center: [30.0222, -1.9596], // starting position [lng, lat]
zoom: 7 // starting zoom
});
map.on('load', () => {
map.addSource('rwanda-provinces', {
'type': 'geojson',
'data':
'https://maplibre.org/maplibre-gl-js/docs/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>