@turf/standard-deviational-ellipse

standardDeviationalEllipse

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][1]
in ArcGIS and the [QGIS Standard Deviational Ellipse Plugin][2]

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}][3].

• 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}][4].

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* points [FeatureCollection][5]<[Point][6]> GeoJSON points
* options [Object][7] Optional parameters (optional, default {})

* options.weight [string][8]? the property name used to weight the center
* options.steps [number][9] number of steps for the polygon (optional, default 64)
* options.properties [Object][7] properties to pass to the resulting ellipse (optional, default {})

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

//addToMap
const addToMap = [points, sdEllipse];
`

Returns [Feature][10]<[Polygon][11]> an elliptical Polygon that includes approximately 1 SD of the dataset within it.

[1]: http://desktop.arcgis.com/en/arcmap/10.3/tools/spatial-statistics-toolbox/directional-distribution.htm

[2]: http://arken.nmbu.no/~havatv/gis/qgisplugins/SDEllipse/

[3]: https://doi.org/10.2307/490885|10.2307/490885}

[4]: https://doi.org/10.1086/214336|10.1086/214336}

[5]: https://tools.ietf.org/html/rfc7946#section-3.3

[6]: https://tools.ietf.org/html/rfc7946#section-3.1.2

[7]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object

[8]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String

[9]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number

[10]: https://tools.ietf.org/html/rfc7946#section-3.2

[11]: https://tools.ietf.org/html/rfc7946#section-3.1.6

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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.

$3

Install this single module individually:

`sh
$ npm install @turf/standard-deviational-ellipse
`

Or install the all-encompassing @turf/turf module that includes all modules as functions:

`sh
$ npm install @turf/turf
``