@turf/sample

What is @turf/sample?

@turf/sample is a module within the Turf.js library, which is a collection of geospatial analysis tools written in JavaScript. The @turf/sample package specifically allows users to sample a specified number of points from a given set of features, such as polygons or lines, within a GeoJSON object.

What are @turf/sample's main functionalities?

Random Point Sampling

This feature allows you to randomly sample a specified number of points from a set of points. In this example, 100 random points are generated within the given bounding box, and then 10 points are sampled from these.

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

const points = turf.randomPoint(100, {bbox: [-180, -90, 180, 90]});
const sampledPoints = sample(points, 10);
console.log(sampledPoints);

Sampling from Polygons

This feature allows you to sample points from within a polygon. In this example, a polygon is defined, 100 random points are generated within the bounding box of the polygon, and then 10 points are sampled from these.

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

const polygon = turf.polygon([[
  [-5, 52], [-4, 52], [-4, 53], [-5, 53], [-5, 52]
]]);
const points = turf.randomPoint(100, {bbox: [-5, 52, -4, 53]});
const sampledPoints = sample(points, 10);
console.log(sampledPoints);

Other packages similar to @turf/sample

geojson-random

The geojson-random package allows users to generate random GeoJSON points, polygons, and lines. While it focuses on generating random features, it does not provide sampling capabilities like @turf/sample.

random-points-on-polygon

This package generates random points within a given polygon. It is similar to @turf/sample in that it can generate points within a polygon, but it does not offer the broader sampling capabilities from various feature sets that @turf/sample provides.

README

@turf/sample

sample

Takes a FeatureCollection and returns a FeatureCollection with given number of features at random.

Parameters

• featurecollection FeatureCollection set of input features
• num number number of features to select

Examples

var points = turf.randomPoint(100, {bbox: [-80, 30, -60, 60]});

var sample = turf.sample(points, 5);

//addToMap
var addToMap = [points, sample]
turf.featureEach(sample, function (currentFeature) {
  currentFeature.properties['marker-size'] = 'large';
  currentFeature.properties['marker-color'] = '#000';
});

Returns FeatureCollection a FeatureCollection with n features

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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/sample

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

$ npm install @turf/turf