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Cluster

CircleCI Go Report Go Doc

gocluster is a very fast Golang library for geospatial point clustering. Benchmarks available below.

This is a fork of GoCluster. Which is basically a port of Mapbox supercluster.

Additional features comparing to the origin:

- Correct grouping when the view covers both hemispheres
- Method to obtain a cluster expansion zoom
- Refactored implementation
- Improved test coverage
- Google maps example

clusters2

The cluster uses hierarchical greedy clustering approach.

Usage example:

package main

import (
  "github.com/aliakseiz/gocluster"
  "log"
)

func main() {
  var points []*cluster.Point
  // Convert slice of your objects to slice of GeoPoint (interface) objects
  geoPoints := make([]cluster.GeoPoint, len(points))
  
  for i := range points {
    geoPoints[i] = points[i]
  }
  // Create new cluster (this will build index)
  c, err := cluster.New(geoPoints, cluster.WithinZoom(0, 21))
  if err != nil {
    log.Fatal(err)
  }

  // Get tour tile with mercator coordinate projections to display directly on the map
  result := c.GetTile(0, 0, 0)
  // or get all clusters for zoom 10 without points count limit
  results := c.AllClusters(10, -1)

  log.Printf("%v\n", result)
  log.Printf("%v\n", results)
}

All IDs of Point that you have as result are the index of initial array of Geopoint, so you could get you point by this index.

Init cluster index

To init the index, points should be prepared first. All points should implement GeoPoint interface:

type GeoPoint interface {
	GetCoordinates() GeoCoordinates
}

type GeoCoordinates struct {
	Lng float64
	Lat float64
}

The Cluster could be tweaked:

parameter default value description
MinZoom 0 Minimum zoom level at which clusters are generated
MaxZoom 16 Minimum zoom level at which clusters are generated
PointSize 40 Cluster radius, in pixels
TileSize 512 Tile extent. Radius is calculated relative to this value
NodeSize 64 NodeSize is size of the KD-tree node. Higher means faster indexing but slower search, and vise versa.

Available option functions:

WithPointSize(size int) Option
WithTileSize(size int) Option
WithinZoom(min, max int) Option
WithNodeSize(size int) Option

// Creating new cluster
New(points []GeoPoint, opts ...Option) (*Cluster, error)

Search point in boundary box

To search all points inside the box, that are limited by the box, formed by north-west point and east-south points. Z index should be provided as well.

northWest := simplePoint{71.36718750000001, -83.79204408779539}
southEast := simplePoint{-71.01562500000001, 83.7539108491127}
zoom := 2

results := c.GetClusters(northWest, southEast, zoom)

Returns the array of 'ClusterPoint' for zoom level. Each point has the following coordinates:

  • X coordinate of returned object is Longitude
  • Y coordinate of returned object is Latitude
  • if the object is cluster of points (NumPoints > 1), the ID is generated started from ClusterIdxSeed (ID> ClusterIdxSeed)
  • if the object represents only one point, it's id is the index of initial GeoPoints array

Search points for tile

OSM and Google maps uses tiles system to optimize map loading. So it is possible to get all points for the tile with tileX, tileY and zoom:

c := NewCluster(geoPoints)
tileX := 0
tileY := 1
zoom := 4

results := c.GetTile(tileX, tileY, zoom)

In this case all coordinates are returned in pixels for that tile. To retrieve objects with Lat, Lng, GetTileWithLatLng method should be used.

Test data

Testdata in testdata directory is based on GeoJSON format.

Benchmarks