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Add support for weighted cluster point calculation #236

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Add support for weighted cluster point calculation #236

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28 changes: 18 additions & 10 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -26,13 +26,14 @@ const OFFSET_ZOOM = 2;
const OFFSET_ID = 3;
const OFFSET_PARENT = 4;
const OFFSET_NUM = 5;
const OFFSET_PROP = 6;
const OFFSET_WEIGHT = 6;
const OFFSET_PROP = 7;

export default class Supercluster {
constructor(options) {
this.options = Object.assign(Object.create(defaultOptions), options);
this.trees = new Array(this.options.maxZoom + 1);
this.stride = this.options.reduce ? 7 : 6;
this.stride = OFFSET_PROP + (this.options.reduce ? 1 : 0);
this.clusterProps = [];
}

Expand Down Expand Up @@ -62,7 +63,8 @@ export default class Supercluster {
Infinity, // the last zoom the point was processed at
i, // index of the source feature in the original input array
-1, // parent cluster id
1 // number of points in a cluster
1, // number of points in a cluster
p.properties?.weight ?? 1 // cluster weight
);
if (this.options.reduce) data.push(0); // noop
}
Expand Down Expand Up @@ -295,17 +297,23 @@ export default class Supercluster {
const numPointsOrigin = data[i + OFFSET_NUM];
let numPoints = numPointsOrigin;

const pointsWeightOrigin = data[i + OFFSET_WEIGHT];
let pointsWeight = pointsWeightOrigin;

// count the number of points in a potential cluster
for (const neighborId of neighborIds) {
const k = neighborId * stride;
// filter out neighbors that are already processed
if (data[k + OFFSET_ZOOM] > zoom) numPoints += data[k + OFFSET_NUM];
if (data[k + OFFSET_ZOOM] > zoom) {
numPoints += data[k + OFFSET_NUM];
pointsWeight += data[k + OFFSET_WEIGHT];
}
}

// if there were neighbors to merge, and there are enough points to form a cluster
if (numPoints > numPointsOrigin && numPoints >= minPoints) {
let wx = x * numPointsOrigin;
let wy = y * numPointsOrigin;
let wx = x * pointsWeightOrigin;
let wy = y * pointsWeightOrigin;

let clusterProperties;
let clusterPropIndex = -1;
Expand All @@ -319,9 +327,9 @@ export default class Supercluster {
if (data[k + OFFSET_ZOOM] <= zoom) continue;
data[k + OFFSET_ZOOM] = zoom; // save the zoom (so it doesn't get processed twice)

const numPoints2 = data[k + OFFSET_NUM];
wx += data[k] * numPoints2; // accumulate coordinates for calculating weighted center
wy += data[k + 1] * numPoints2;
const pointsWeight2 = data[k + OFFSET_WEIGHT];
wx += data[k] * pointsWeight2; // accumulate coordinates for calculating weighted position
wy += data[k + 1] * pointsWeight2;

data[k + OFFSET_PARENT] = id;

Expand All @@ -336,7 +344,7 @@ export default class Supercluster {
}

data[i + OFFSET_PARENT] = id;
nextData.push(wx / numPoints, wy / numPoints, Infinity, id, -1, numPoints);
nextData.push(wx / pointsWeight, wy / pointsWeight, Infinity, id, -1, numPoints, pointsWeight);
if (reduce) nextData.push(clusterPropIndex);

} else { // left points as unclustered
Expand Down