95 lines
3.2 KiB
Markdown
95 lines
3.2 KiB
Markdown
# @turf/standard-deviational-ellipse
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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
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## standardDeviationalEllipse
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Takes a [FeatureCollection][1] and returns a standard deviational ellipse,
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also known as a “directional distribution.” The standard deviational ellipse
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aims to show the direction and the distribution of a dataset by drawing
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an ellipse that contains about one standard deviation’s worth (~ 70%) of the
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data.
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This module mirrors the functionality of [Directional Distribution][2]
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in ArcGIS and the [QGIS Standard Deviational Ellipse Plugin][3]
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**Bibliography**
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• Robert S. Yuill, “The Standard Deviational Ellipse; An Updated Tool for
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Spatial Description,” _Geografiska Annaler_ 53, no. 1 (1971): 28–39,
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doi:[10.2307/490885][4].
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• Paul Hanly Furfey, “A Note on Lefever’s “Standard Deviational Ellipse,”
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_American Journal of Sociology_ 33, no. 1 (1927): 94—98,
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doi:[10.1086/214336][5].
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**Parameters**
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- `points` **[FeatureCollection][6]<[Point][7]>** GeoJSON points
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- `options` **[Object][8]** Optional parameters (optional, default `{}`)
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- `options.weight` **[string][9]?** the property name used to weight the center
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- `options.steps` **[number][10]** number of steps for the polygon (optional, default `64`)
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- `options.properties` **[Object][8]** properties to pass to the resulting ellipse (optional, default `{}`)
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**Examples**
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```javascript
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var bbox = [-74, 40.72, -73.98, 40.74];
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var points = turf.randomPoint(400, {bbox: bbox});
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var sdEllipse = turf.standardDeviationalEllipse(points);
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//addToMap
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var addToMap = [points, sdEllipse];
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```
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Returns **[Feature][11]<[Polygon][12]>** an elliptical Polygon that includes approximately 1 SD of the dataset within it.
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[1]: https://tools.ietf.org/html/rfc7946#section-3.3
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[2]: http://desktop.arcgis.com/en/arcmap/10.3/tools/spatial-statistics-toolbox/directional-distribution.htm
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[3]: http://arken.nmbu.no/~havatv/gis/qgisplugins/SDEllipse/
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[4]: https://doi.org/10.2307/490885
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[5]: https://doi.org/10.1086/214336
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[6]: https://tools.ietf.org/html/rfc7946#section-3.3
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[7]: https://tools.ietf.org/html/rfc7946#section-3.1.2
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[8]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object
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[9]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String
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[10]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number
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[11]: https://tools.ietf.org/html/rfc7946#section-3.2
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[12]: https://tools.ietf.org/html/rfc7946#section-3.1.6
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<!-- This file is automatically generated. Please don't edit it directly:
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if you find an error, edit the source file (likely index.js), and re-run
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./scripts/generate-readmes in the turf project. -->
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---
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This module is part of the [Turfjs project](http://turfjs.org/), an open source
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module collection dedicated to geographic algorithms. It is maintained in the
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[Turfjs/turf](https://github.com/Turfjs/turf) repository, where you can create
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PRs and issues.
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### Installation
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Install this module individually:
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```sh
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$ npm install @turf/standard-deviational-ellipse
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```
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Or install the Turf module that includes it as a function:
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```sh
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$ npm install @turf/turf
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```
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