@jetblack/cluster-manager
v2.0.0
Published
A geospatial point clustering library.
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@jetblack/cluster-manager
A geospatial cluster manager (read the docs).
When a zoomable map contains a large number of points the map becomes cluttered and the performance is degraded when zoomed out. The cluster manager organizes the points into clusters where nearby points are combined into a single cluster.
This package is based on the widely used and battle tested supercluster (which is probably what you should be using). This package differs in three ways.
- It represents the data as a tree of nodes to make the structure directly accessible.
- The points don't have to be presented in a specific shape, but take a "getter" function to get the coordinate from the a point.
- The world is wrap-around (i.e. a point on the far west equator is considered close to a point on the far east equator).
Installation
The package can be installed from npmjs.
npm install --save @jetblack/cluster-manager
Usage
The following example shows how to use the cluster manager with geojson point features.
import { ClusterManager } from '@jetblack/cluster-manager'
// The data.
const features = {
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"properties": {
"name": "Greenwich Observatory"
},
"geometry": {
"type": "Point",
"coordinates": [-0.000526, 51.476847]
}
},
{
"type": "Feature",
"properties": {
"name": "Buckingham Palace"
},
"geometry": {
"type": "Point",
"coordinates": [-0.141826, 51.501200]
}
},
]
}
// Rather than requiring a specific format for the data, a function to
// return the coordinates from a data item is provided.
const getCoordinates = (point) => ({
latitude: point.geometry.coordinates[1],
longitude: point.geometry.coordinates[0],
});
// This function is used to make the point data when a node cluster
// is generated.
const makePoint = (coordinate, nodes) => ({
type: "Feature",
geometry: {
type: "Point",
coordinates: [coordinate.longitude, coordinate.latitude],
},
properties: {
type: "cluster",
name: ",".join(nodes.flatMap(n => n.leaves()).map(n => n.data.properties.name))
count: sum(nodes.map((node) => node.count())),
},
});
// Create the cluster manager
const clusterManager = new ClusterManager(pointFeatures, getCoordinates, makePoint)
// Set the bounds to be the whole world to get all the clusters.
const bounds = {
northWest: { latitude: 90, longitude: -180 },
southEast: { latitude: -90, longitude: 180 }
}
const zoom = 2
// Get the clustered nodes for a zoom level and bounds.
const cluster = clusterManager.getCluster(bounds, zoom)
// The cluster is an array of nodes. The "data" property holds the original
// data for the leaves, and the generated data for the cluster nodes. The
// "nodes" property has an array of the contained nodes. The "leaf" method
// returns the leaf nodes.
for (const node of cluster) {
console.log(node.data.properties.name)
for (leaf of node.leaves()) {
console.log(leaf.data.properties.name)
}
}
Acknowledgements
THis code was built on the work of supercluster.