89 lines
2.5 KiB
Markdown
89 lines
2.5 KiB
Markdown
# @turf/union
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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
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## union
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Takes a collection of input polygons and returns a combined polygon. If the
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input polygons are not contiguous, this function returns a multi-polygon
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feature.
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### Parameters
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* `features` **[FeatureCollection][1]<([Polygon][2] | [MultiPolygon][3])>** input polygon features
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* `options` **[Object][4]** Optional Parameters (optional, default `{}`)
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* `options.properties` **[GeoJsonProperties][5]** properties to assign to output feature (optional, default `{}`)
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### Examples
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```javascript
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const poly1 = turf.polygon(
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[
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[
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[-82.574787, 35.594087],
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[-82.574787, 35.615581],
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[-82.545261, 35.615581],
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[-82.545261, 35.594087],
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[-82.574787, 35.594087],
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],
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],
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{ fill: "#0f0" }
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);
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const poly2 = turf.polygon(
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[
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[
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[-82.560024, 35.585153],
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[-82.560024, 35.602602],
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[-82.52964, 35.602602],
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[-82.52964, 35.585153],
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[-82.560024, 35.585153],
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],
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],
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);
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const union = turf.union(turf.featureCollection([poly1, poly2]));
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//addToMap
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const addToMap = { poly1, poly2, union };
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poly1.properties.fill = "#0f0";
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poly2.properties.fill = "#00f";
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union.properties.stroke = "red";
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union.properties["stroke-width"] = 4;
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union.properties.fill = "transparent";
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```
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Returns **([Feature][5]<([Polygon][2] | [MultiPolygon][3])> | null)** a combined polygon or multi-polygon feature, or null if there were no input polygons to combine
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[1]: https://tools.ietf.org/html/rfc7946#section-3.3
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[2]: https://tools.ietf.org/html/rfc7946#section-3.1.6
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[3]: https://tools.ietf.org/html/rfc7946#section-3.1.7
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[4]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object
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[5]: https://tools.ietf.org/html/rfc7946#section-3.2
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<!-- This file is automatically generated. Please don't edit it directly. If you find an error, edit the source file of the module in question (likely index.js or index.ts), and re-run "yarn docs" from the root of the turf project. -->
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---
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This module is part of the [Turfjs project](https://turfjs.org/), an open source module collection dedicated to geographic algorithms. It is maintained in the [Turfjs/turf](https://github.com/Turfjs/turf) repository, where you can create PRs and issues.
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### Installation
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Install this single module individually:
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```sh
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$ npm install @turf/union
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```
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Or install the all-encompassing @turf/turf module that includes all modules as functions:
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```sh
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$ npm install @turf/turf
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```
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