@turf/concave

What is @turf/concave?

@turf/concave is a module within the Turf.js library that allows you to generate concave hull polygons from a set of points. This can be useful for creating boundaries that more closely fit the shape of the input points compared to convex hulls.

What are @turf/concave's main functionalities?

Generate Concave Hull

This feature allows you to generate a concave hull polygon from a set of points. The `maxEdge` parameter controls the maximum length of an edge in the hull, which influences the 'concaveness' of the resulting polygon.

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

const points = turf.featureCollection([
  turf.point([10, 10]),
  turf.point([20, 20]),
  turf.point([30, 10]),
  turf.point([40, 40]),
  turf.point([50, 30])
]);

const concaveHull = turf.concave(points, {maxEdge: 25});

console.log(JSON.stringify(concaveHull));

Other packages similar to @turf/concave

hull.js

Hull.js is a JavaScript library for computing the convex hull of a set of 2D points. Unlike @turf/concave, which generates concave hulls, hull.js focuses on convex hulls, which are simpler and faster to compute but may not fit the shape of the input points as closely.

concaveman

Concaveman is a very fast 2D concave hull algorithm. It is similar to @turf/concave in that it generates concave hulls, but it is optimized for performance and simplicity. It may not offer as many configuration options as @turf/concave.

README

@turf/concave

concave

Takes a set of points and returns a concave hull Polygon or MultiPolygon. Internally, this uses turf-tin to generate geometries.

Parameters

• points FeatureCollection<Point> input points
• options Object Optional parameters (optional, default {})
  • options.maxEdge number the length (in 'units') of an edge necessary for part of the hull to become concave. (optional, default Infinity)
  • options.units string can be degrees, radians, miles, or kilometers (optional, default 'kilometers')

Examples

var points = turf.featureCollection([
  turf.point([-63.601226, 44.642643]),
  turf.point([-63.591442, 44.651436]),
  turf.point([-63.580799, 44.648749]),
  turf.point([-63.573589, 44.641788]),
  turf.point([-63.587665, 44.64533]),
  turf.point([-63.595218, 44.64765])
]);
var options = {units: 'miles', maxEdge: 1};

var hull = turf.concave(points, options);

//addToMap
var addToMap = [points, hull]

Returns (Feature<(Polygon | MultiPolygon)> | null) a concave hull (null value is returned if unable to compute hull)

---

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/concave

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)