@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

---

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

Changelog

6.2.0

After a bit of hiatus, TurfJS is resuming releases.

⭐️ Major Updates

• ES Modules available for all packages
• Tree shaking should significantly reduce import size of @turf/turf
• Better support for ESM modules (PR https://github.com/Turfjs/turf/pull/1942 - Author @diachedelic)
• Clean-up of test and benchmark running to make publishing easier
• Enforce styling using Prettier
• Enable ESLint and get rid of unused variables
• Upgrade rollup for more correct javascript module builds
• Only include ES5 code

🚀 New Modules

[@turf/boolean-touches][boolean-touches]

Determines if two features touch but do not intersect

[@turf/boolean-valid][boolean-valid]

Checks if the geometry is a valid according to the OGC Simple Feature Specification

[@turf/quadrat-analysis][quadrat-analysis]

Performs a quadrat analysis on a set of points

[@turf/rectangle-grid][rectangle-grid]

Creates a grid of rectangles from a bounding box

[@turf/voroni][voronoi]

Typescript types for the options parameter have been fixed (PR https://github.com/Turfjs/turf/pull/1424 - Author @stevage)

[@turf/points-within-polygon][points-within-polygon]

Typescript types around the Feature's Properties will now be preserved. (PR https://github.com/Turfjs/turf/pull/1761 - Author @rugheid)

[@turf/rewind][rewind]

Typescript types for the 'reverse' option are now correct. Previously it was misnamed as 'reversed'. (PR https://github.com/Turfjs/turf/pull/1786 - Author @jonnycornwell)

[@turf/difference][difference]

No longer publishes an .mjs file.

[@turf/meta][meta]

No longer publishes an .mjs file.

[@turf/tag][tag]

Add MultiPolygon support. (PR https://github.com/Turfjs/turf/pull/1996 - Author bryceroney)

🐛 Bug Fixes

• @turf/centroid Don't visit first point twice when calculating centroid (PR https://github.com/Turfjs/turf/pull/1894 - Author @rowanwins)

• @turf/transform-translate Better handling of negative distances (PR https://github.com/Turfjs/turf/pull/1895 - Author @rowanwins)

• @turf/union, @turf/difference, @turf/intersect Use polygon-clipping library to fix correctness issues (PR https://github.com/Turfjs/turf/pull/1916 - Authors @mbullington, @ngottlieb)

• @turf/buffer Change default number of steps to 8, and actually support the steps option (PR https://github.com/Turfjs/turf/pull/1931 - Author stevenchanin)

• @turf/buffer Fix projection issues that produce undersized buffers at non-equatorial latitudes (PR https://github.com/Turfjs/turf/pull/1956 - Author dyakovlev)

• @turf/helpers Add runtime checks to point() method, fixing an API break (PR https://github.com/Turfjs/turf/pull/1964)

🏅 New Features/Enhancements

• @turf/boolean-overlap Better performance for MultiPoint geometries (PR https://github.com/Turfjs/turf/pull/1910 - Author @mfedderly)

• @turf/helpers Add hectares to convertArea (PR https://github.com/Turfjs/turf/pull/1943 - Author @DanielJDufour)

• @turf/great-circle Update Typescript types to support MultiLineString input (PR https://github.com/Turfjs/turf/pull/1928 - Author kronick)

📖 Documentation

• @turf/square-grid Clarify inputs (PR https://github.com/Turfjs/turf/pull/1885 - Author @raphael-leger)

• @turf/greater-circle Clarify properties option example (PR https://github.com/Turfjs/turf/pull/1888 - Author @chris-catignani)

⚠️ Breaking Change

• @turf/line-to-polygon no longer modifies its input unless the mutate option is true (PR https://github.com/Turfjs/turf/pull/1879 - Author @MortenBirk)

• @turf/unkink-polygon remove Number.prototype.modulo override (PR https://github.com/Turfjs/turf/pull/1978)