ahazrat / leaflet-choropleth

Choropleth plugin for Leaflet (color scale based on value)

Leaflet Choropleth

Choropleth plugin for Leaflet (color scale based on value) - Demo

This plugin extends L.geoJson, giving each feature a style.fillColor that corresponds to a specified value in its properties object. For information on how to use L.geoJson, see the Leaflet tutorial and documentation.

While Leaflet provides a choropleth tutorial, that approach requires you to specify exact breakpoints and colors. This plugin uses chroma.js to abstract that for you. Just tell it which property in the GeoJSON to use and some idea of the color scale you want.

Usage

L.choropleth(geojsonData, {
	valueProperty: 'incidents', // which property in the features to use
	scale: ['white', 'red'], // chroma.js scale - include as many as you like
	steps: 5, // number of breaks or steps in range
	mode: 'q', // q for quantile, e for equidistant, k for k-means
	style: {
		color: '#fff', // border color
		weight: 2,
		fillOpacity: 0.8
	},
	onEachFeature: function(feature, layer) {
		layer.bindPopup(feature.properties.value)
	}
}).addTo(map)

Advanced

• colors: If you prefer to specify your own exact colors, use colors: ['#fff', '#777', ...] instead of scale. Just make sure the number of colors is the same as the number of steps specified.
• valueProperty: To use computed values (such as standardizing), you can use a function for valueProperty that is passed (feature) and returns a number (example).

Installation

• via NPM: npm install leaflet-choropleth
• via Bower: bower install leaflet-choropleth

Include dist/choropleth.js from this repository on your page after Leaflet:

<script src="path/to/leaflet.js"></script>
<script src="path/to/choropleth.js"></script>

Or, if using via CommonJS (Browserify, Webpack, etc.):

var L = require('leaflet')
require('leaflet-choropleth')

Examples

• Basic usage
• Legend
• Fetch & join
• Computed values

Development

This project uses webpack to build the JavaScript and standard for code style linting.

• While developing, use npm run watch to automatically rebuild when files are saved
• Use npm test to run unit tests and code style linter
• Before committing dist/, use npm run build to optimize and minify for production use