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Feature: get zoom level where a point gets unclustered #205

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Feature: get zoom level where a point gets unclustered #205

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8476d83
create function to get the zoom level where a point gets unclustered
B0rk3 Sep 1, 2022
b825ae1
improved logic of getPointUnclusterZoom function
B0rk3 Sep 5, 2022
033a66c
minor bug fix to prevent exceeding the max zoom level
B0rk3 Sep 16, 2022
bd821fd
Merge branch 'mapbox:main' into main
B0rk3 Apr 26, 2023
94ed77d
updates getPointUnclusterZoom function to latest supercluster version
Apr 26, 2023
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4 changes: 4 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,10 @@ and `offset` is the amount of points to skip (for pagination).

Returns the zoom on which the cluster expands into several children (useful for "click to zoom" feature) given the cluster's `cluster_id`.

#### `getPointUnclusterZoom(point)`

Returns the zoom on which a point appears unclustered. The point must be provided as array with `[Lng, Lat]`.

## Options

| Option | Default | Description |
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21 changes: 21 additions & 0 deletions index.js
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Expand Up @@ -167,6 +167,27 @@ export default class Supercluster {
return expansionZoom;
}

getPointUnclusterZoom(point) {
const [lng, lat] = point;
const pointX = fround(lngX(lng));
const pointY = fround(latY(lat));

let expansionZoom = 0;
while (expansionZoom <= this.options.maxZoom) {
const tree = this.trees[expansionZoom];

const unclustered = tree.points.some(
treePoint => !treePoint.id && treePoint.x === pointX && treePoint.y === pointY
);
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This essentially loops through all clusters across all zooms until it reaches the unclustered point, in many instances iterating over nearly the whole dataset. I think we could implement this much more efficiently, utilizing the R-tree indices — e.g. only look at clusters within radius of the point.

Also, what if the point does have id? This filter doesn't look right...

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Thank you for your review and advises!

I improved the code and used the within function of KDBush to filter all points that don't have the same coordinate as the provided point, by setting radius to 0.

I mistakenly assumed that only clusters have an id, so I wanted to filter them first. The value of the parentId should be better suited for this.

Additionally the expansionZoom now starts at the minZoom level, instead of 0, to avoid getting undefined trees entries.

If you have some other advises for improvements, please let me know.


if (unclustered) return expansionZoom;

expansionZoom++;
}

return expansionZoom;
}

_appendLeaves(result, clusterId, limit, offset, skipped) {
const children = this.getChildren(clusterId);

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