# @turf/collect

# collect

Merges a specified property from a FeatureCollection of points into a
FeatureCollection of polygons. Given an `inProperty` on points and an `outProperty`
for polygons, this finds every point that lies within each polygon, collects the
`inProperty` values from those points, and adds them as an array to `outProperty`
on the polygon.

**Parameters**

-   `polygons` **[FeatureCollection](http://geojson.org/geojson-spec.html#feature-collection-objects)<[Polygon](http://geojson.org/geojson-spec.html#polygon)>** polygons with values on which to aggregate
-   `points` **[FeatureCollection](http://geojson.org/geojson-spec.html#feature-collection-objects)<[Point](http://geojson.org/geojson-spec.html#point)>** points to be aggregated
-   `inProperty` **[string](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)** property to be nested from
-   `outProperty` **[string](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)** property to be nested into

**Examples**

```javascript
var poly1 = turf.polygon([[[0,0],[10,0],[10,10],[0,10],[0,0]]]);
var poly2 = turf.polygon([[[10,0],[20,10],[20,20],[20,0],[10,0]]]);
var polyFC = turf.featureCollection([poly1, poly2]);
var pt1 = turf.point([5,5], {population: 200});
var pt2 = turf.point([1,3], {population: 600});
var pt3 = turf.point([14,2], {population: 100});
var pt4 = turf.point([13,1], {population: 200});
var pt5 = turf.point([19,7], {population: 300});
var pointFC = turf.featureCollection([pt1, pt2, pt3, pt4, pt5]);
var collected = turf.collect(polyFC, pointFC, 'population', 'values');
var values = collected.features[0].properties.values
//=values => [200, 600]

//addToMap
var addToMap = [pointFC, collected]
```

Returns **[FeatureCollection](http://geojson.org/geojson-spec.html#feature-collection-objects)<[Polygon](http://geojson.org/geojson-spec.html#polygon)>** polygons with properties listed based on `outField`

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---

This module is part of the [Turfjs project](http://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.

### Installation

Install this module individually:

```sh
$ npm install @turf/collect
```

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

```sh
$ npm install @turf/turf
```