@spatial/standard-deviational-ellipse

standardDeviationalEllipse

Takes a FeatureCollection 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: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:10.1086/214336.

Parameters

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

Examples

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

//addToMap
var addToMap = [points, sdEllipse];

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

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 @spatial/standard-deviational-ellipse

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

$ npm install @turf/turf