代码之家 › 专栏 › 技术社区 › Fractaliste

如何使用mapbox的集群设置reduce选项?

mapbox javascript

Fractaliste · 技术社区 · 7 年前

我在用Mabbox GL JS v0.45进行POC集群。

我想自定义集群的属性(实际默认值为point_count和point_count_缩写)。我的每个点(每个城市一个)都有一个曲面属性(一个整数),我想在点聚集时求和。

我明白了 mapbox's sources 用于计算自定义属性的reduce函数的引用:

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}; },
    },

但是我在文件上没有看到任何关于它的提及。 如何设置这些选项?

mapbox似乎没有发布这些接口( see cluster's documentation )没有提到 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)
});

2 回复 | 直到 7 年前

Fractaliste 7 年前

有人给了我一个解决方法:不要使用嵌入的supcluster,而是创建自己的并将其用作源:

var myCluster = supercluster({
    radius: 40,
    maxZoom: 16,
    reduce: function(p) { /* I can use reduce/map/... functions! */ }
});

// My clustered source is created without Mapbox's clusters since I managed my clusters outside Mapbox library.
map.addSource("earthquakes", {
    type: "geojson",
    data : {
      "type" : "FeatureCollection",
      "features" : []
    }
});

function loadRemoteGeoJson() {
    var features
    // Do what you want, when you want to retrieve remote features...
    // ...
    // In the end set features into your supercluster
    myCluster.load(features)
    pushClusterIntoMapbox(map)
}

// Function to call when you load remote data AND when you zoom in or out !
function pushClusterIntoMapbox(map) {
  // I maybe should be bounded here...
  var clusters = myCluster.getClusters([ -180.0000, -90.0000, 180.0000, 90.0000 ], Math
      .floor(map.getZoom()))

  // My colleague advice me to use http://turfjs.org as helper but I think it's quite optionnal
  var features = turf.featureCollection(clusters)
  map.getSource("earthquakes").setData(features)
}

Jivings 7 年前

它看起来像是一个规则的减量。它将为每个点调用一个,并允许您使用点的属性为集群整体创建属性。

所以如果你这样定义你的减量;

supercluster({
  reduce: (clusterProps, pointProps) => {
    clusterProps.sum += pointProps.surface;
  }
});

然后 sum 群集上的属性将是所有 surface 点的属性。