I'm POC-ing clusters with Mabpox-gl-js v0.45.
I would like to customize my cluster's properties (actual default values are point_count and point_count_abbreviated). Each of my points (one for each city) have a surface property (an integer) which I want to sum when points are clustered.
I see in mapbox's sources a reference to a reduce function to calculate custom properties:
SuperCluster.prototype = { options: { minZoom: 0, // min zoom to generate clusters on // ..... log: false, // whether to log timing info // a reduce function for calculating custom cluster properties reduce: null, // function (accumulated, props) { accumulated.sum += props.sum; } // initial properties of a cluster (before running the reducer) initial: function () { return {}; }, // function () { return {sum: 0}; }, // properties to use for individual points when running the reducer map: function (props) { return props; } // function (props) { return {sum: props.my_value}; }, }, But I don't see any mention about it on the documentation. How can I set these options?
Mapbox seems not to publish these interface (see cluster's documentation) and no mention are done on provided exemple:
map.addSource("earthquakes", { type: "geojson", // Point to GeoJSON data. This example visualizes all M1.0+ earthquakes // from 12/22/15 to 1/21/16 as logged by USGS' Earthquake hazards program. data: "/mapbox-gl-js/assets/earthquakes.geojson", cluster: true, clusterMaxZoom: 14, // Max zoom to cluster points on clusterRadius: 50 // Radius of each cluster when clustering points (defaults to 50) }); 1 Answers
Answers 1
It looks as if it works like a regular reduce. It will be called one for each point, and allows you to use the properties of the point to create properties for the cluster overall.
So if you define your reduce like this;
supercluster({ reduce: (clusterProps, pointProps) => { clusterProps.sum += pointProps.surface; } }); Then the sum property on the cluster will be the sum of all the surface properties on the points.
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