@turf/collect

What is @turf/collect?

@turf/collect is a module from the Turf.js library that allows you to collect properties from one set of features (points) and aggregate them into another set of features (polygons). This is particularly useful for spatial analysis tasks where you need to summarize or aggregate data based on spatial relationships.

What are @turf/collect's main functionalities?

Collect properties from points into polygons

This feature allows you to collect properties from a set of point features and aggregate them into polygon features. In this example, the population property from the points is collected into the polygons.

const turf = require('@turf/turf');

const points = turf.featureCollection([
  turf.point([0, 0], {population: 200}),
  turf.point([2, 2], {population: 300}),
  turf.point([2, 0], {population: 150})
]);

const polygons = turf.featureCollection([
  turf.polygon([[
    [0, 0], [2, 0], [2, 2], [0, 2], [0, 0]
  ]], {name: 'polygon1'})
]);

const collected = turf.collect(polygons, points, 'population', 'collectedPopulations');
console.log(JSON.stringify(collected, null, 2));

Other packages similar to @turf/collect

geostats

The geostats package provides a range of statistical functions for geospatial data, including classification and aggregation. While it does not directly offer the same point-to-polygon aggregation as @turf/collect, it can be used for similar statistical analysis tasks on geospatial data.

jsts

The jsts (JavaScript Topology Suite) package offers a wide range of spatial analysis and geometry operations. It includes functionalities for spatial relationships and operations, but it is more complex and lower-level compared to the specific point-to-polygon aggregation provided by @turf/collect.

README

@turf/collect

collect

Joins attributes FeatureCollection of polygons with a FeatureCollection of points. Given an inProperty on points and an outProperty for polygons, this finds every point that lies within each polygon, collects the inProperty values from those points, and adds them as an array to outProperty on the polygon.

Parameters

• polygons FeatureCollection<Polygon> polygons with values on which to aggregate
• points FeatureCollection<Point> points to be aggregated
• inProperty string property to be nested from
• outProperty string property to be nested into

Examples

var poly1 = polygon([[[0,0],[10,0],[10,10],[0,10],[0,0]]]);
var poly2 = polygon([[[10,0],[20,10],[20,20],[20,0],[10,0]]]);
var polyFC = featurecollection([poly1, poly2]);
var pt1 = point([5,5], {population: 200});
var pt2 = point([1,3], {population: 600});
var pt3 = point([14,2], {population: 100});
var pt4 = point([13,1], {population: 200});
var pt5 = point([19,7], {population: 300});
var ptFC = featurecollection([pt1, pt2, pt3, pt4, pt5]);
var aggregated = aggregate(polyFC, ptFC, 'population', 'values');

aggregated.features[0].properties.values // => [200, 600]);

Returns FeatureCollection<Polygon> polygons with properties listed based on outField

---

This module is part of the Turfjs project, an open source module collection dedicated to geographic algorithms. It is maintained in the Turfjs/turf repository, where you can create PRs and issues.

Installation

Install this module individually:

$ npm install @turf/collect

Or install the Turf module that includes it as a function:

$ npm install @turf/turf