standardDeviationalEllipse

Description

Takes a collection of features and returns a standard deviational ellipse, also known as a “directional distribution.” The standard deviational ellipse aims to show the direction and the distribution of a dataset by drawing an ellipse that contains about one standard deviation’s worth (~ 70%) of the data.

This module mirrors the functionality of Directional Distribution in ArcGIS and the QGIS Standard Deviational Ellipse Plugin

Bibliography

• Robert S. Yuill, “The Standard Deviational Ellipse; An Updated Tool for Spatial Description,” Geografiska Annaler 53, no. 1 (1971): 28–39, doi:{@link [https://doi.org/10.2307/490885 | 10.2307/490885}](https://doi.org/10.2307/490885 | 10.2307/490885}).

• Paul Hanly Furfey, “A Note on Lefever’s “Standard Deviational Ellipse,” American Journal of Sociology 33, no. 1 (1927): 94—98, doi:{@link [https://doi.org/10.1086/214336 | 10.1086/214336}](https://doi.org/10.1086/214336 | 10.1086/214336}).

Parameters

Name	Type	Description
points	FeatureCollection<Point>	GeoJSON points
options?	Object	Optional parameters (default {})
options.weight?	string	the property name used to weight the center
options.steps?	number	number of steps for the polygon (default 64)
options.properties?	Object	properties to pass to the resulting ellipse (default {})

Returns

Feature<Polygon> an elliptical Polygon that includes approximately 1 SD of the dataset within it.

Examples

const bbox = [-74, 40.72, -73.98, 40.74];
const points = turf.randomPoint(400, { bbox: bbox });
const sdEllipse = turf.standardDeviationalEllipse(points);

Installation

$ npm install @turf/standard-deviational-ellipse

import { standardDeviationalEllipse } from "@turf/standard-deviational-ellipse";
const result = standardDeviationalEllipse(...);

$ npm install @turf/turf

import * as turf from "@turf/turf";
const result = turf.standardDeviationalEllipse(...);