turf

turf

a fast and fully featured open gis engine written in javascript

---

##Installation

npm install turf

Turf can also be run in a browser. To use it, download the minified file, and include it in a script tag.

NOTE: Browser functionality is currently unstable. Please consider using turf from node.js. Work is in progress on resolving the issues.

<script src="turf.min.js"></script>

It can also be installed using bower:

bower install turf

---

##Features

####geometry

• load
• save
• point
• linestring
• polygon
• featurecollection

####joins

• inside
• within
• tag

####data

• remove
• filter
• sample

####measurement

• distance
• nearest
• bboxPolygon
• envelope
• extent
• square
• size
• center
• centroid
• midpoint

####interpolation

• tin
• grid
• planepoint
• contour
• isolines
• isobands

####classification

• quantile
• jenks
• reclass

####aggregation

• average
• median
• sum
• min
• max
• count
• deviation
• variance
• aggregate

####transformation

• buffer
• bezier
• simplify
• union
• merge
• intersect
• erase
• donuts
• convex
• concave

####misc

• flip
• explode
• combine
• isClockwise

Planned Features

Additional feature requests welcomed and encouraged. To request a feature, please add a github issue with a description.

• clockwise
• krige
• cluster
• interval
• cluster
• area
• smooth

---

##Examples:

###load

Loads a Feature or FeaturCollection from a file.

var t = require('turf')
geojsonFile = '/path/to/file/tress.geojson'

t.load(geoJsonFile, function(err, trees){
  if(err) throw err
  console.log(trees)
})

###save

Saves out a feature or feature collection. 'geojson' and 'topojson' are currently supported.

var path = './testOut/poly.geojson'
var poly = t.polygon([[[0,0], [1,0], [1,1],[0,1]]])
var type = 'geojson'
t.save(path, poly, type, function(err, res){
  if(err) throw err
  console.log(res) // 1
  done()
})

###point

Creates a geojson point Feature based on an x and a y coordinate. Properties can be added optionally.

var t = require('turf')

var point1 = t.point(-75.343, 39.984)
var point2 = t.point(-75.343, 39.984, {name: 'point 1', population: 5000})
console.log(point1)
console.log(point2)

###linestring

Creates a geojson linestring Feature based on a coordinate array. Properties can be added optionally.

var t = require('turf')

var linestring1 = t.linestring([[102.0, -10.0], [103.0, 1.0], [104.0, 0.0], [130.0, 4.0]])
var linestring2 = t.linestring([[102.0, -10.0], [103.0, 1.0], [104.0, 0.0], [130.0, 4.0]],
  {name: 'line 1', distance: 145})
console.log(linestring1)
console.log(linestring2)

###polygon

Creates a geojson polygon Feature based on a coordinate array. Properties can be added optionally.

var t = require('turf')

var polygon1 = t.point([[[20.0,0.0],[101.0,0.0],[101.0,1.0],[100.0,1.0],[100.0,0.0]]])
var polygon2 = t.point([[[20.0,0.0],[101.0,0.0],[101.0,1.0],[100.0,1.0],[100.0,0.0]]],
  {name: 'line 1', distance: 145})
console.log(polygon1)
console.log(polygon2)

###featurecollection

Creates a geojson FeatureCollection based on an array of features.

var t = require('turf')
var pt1 = t.point(-75.343, 39.984, {name: 'Location A'})
var pt2 = t.point(-75.833, 39.284, {name: 'Location B'})
var pt3 = t.point(-75.534, 39.123, {name: 'Location C'})

var fc = t.featurecollection([pt1, pt2, pt3])
console.log(fc)

###extent

Calculates the extent of all features and returns a bounding box.

var t = require('turf')

t.load('path/to/file/example.geojson', function(err, features){
  if(err) throw err
  t.extent(features, function(extent){
    console.log(extent) // [minX, minY, maxX, maxY]
  })
})

###square

Calculates the minimum square bounding box for another bounding box.

var t = require('turf')
var bbox = [0,0,5,10]]

t.square(bbox, function(err, square){
  if(err) throw err
  console.log(square) // [-2.5, 0, 7.5, 10]
})

###size

Takes a bbox and returns a new bbox with a size expanded or contracted by a factor of X.

var bbox = [0, 0, 10, 10]

t.size(bbox, 2, function(err, doubled){
  if(err) throw err
  console.log(doubled) // [-10, -10, 20, 20]
})

###center

Calculates the absolute center point of all features.

var t = require('turf')

t.load('path/to/file/example.geojson', function(layer, err){
  if(err) throw err
  t.center(layer, function(center){
    console.log(center)
  })
})

###bboxPolygon

Takes a bbox and returns the equivalent polygon feature.

var t = require('turf')
var bbox = [0,0,10,10]

t.bboxPolygon(bbox, function(err, poly){
  if(err) throw err
  console.log(poly)
})

###envelope

Takes a Feature or FeatureCollection and returns a rectangular polygon feature that encompasses all vertices.

var t = require('turf')
var pt1 = t.point(-75.343, 39.984, {name: 'Location A'})
var pt2 = t.point(-75.833, 39.284, {name: 'Location B'})
var pt3 = t.point(-75.534, 39.123, {name: 'Location C'})
var fc = t.featurecollection([pt1, pt2, pt3])

t.envelope(fc, function(err, envelopePoly){
  if(err) throw err
  console.log(envelopePoly)
})

###centroid

Calculates the centroid of a polygon Feature or FeatureCollection using the geometric mean of all vertices. This lessons the effect of small islands and artifacts when calculating the centroid of a set of polygons.

var t = require('turf')
var poly = t.polygon([[[0,0], [0,10], [10,10] , [10,0]]])

t.centroid(poly, function(err, centroid){
  if(err) throw err
  console.log(centroid) // a point at 5, 5
})

###flip

Takes a point, linestring, polygon, or featurecollection, and flips all of its coordinates from [x, y] to [y, x].

var t = require('turf')

var poly = t.polygon([[[1,0], [1,0], [1,2]], [[.2,.2], [.3,.3],[.1,.2]]])
t.flip(poly, function(err, flipped){
  if(err) throw err
  console.log(flipped)
})

###explode

Takes a Feature or FeatureCollection and return all vertices as a collection of points.

var t = require('turf')
var poly = t.polygon([[[0,0], [0,10], [10,10] , [10,0]]])

t.explode(poly, function(err, vertices){
  if(err) throw err
  console.log(vertices)
})

###combine

Combines feature collection of point, linestring, or polygon features into multipoint, multilinestring, or multipolygon features.

var t = require('turf')
var pt1 = t.point(50, 1)
var pt2 = t.point(100, 101)
var fc = t.featurecollection([pt1, pt2])

t.combine(fc, function(err, combined){
  if(err) throw err
  console.log(combined)
})

###isClockwise

Takes a ring and return true or false whether or not the ring is clockwise or counter-clockwise.

var t = require('turf')
var clockwiseRing = [[0,0],[1,1],[1,0],[0,0]]
var counterClockwiseRing = [[0,0],[1,0],[1,1],[0,0]]

var clockwise = t.isClockwise(clockwiseRing)
var counterClockwise = t.isClockwise(counterClockwiseRing)

console.log(clockwise) // true
console.log(counterClockwise) // false

###remove

Removes any features from a feature collection that match a property value.

var t = require('turf')
var trees = t.featurecollection([t.point(1,2, {species: 'oak'}),
                                 t.point(2,1, {species: 'dogwood'}),
                                 t.point(3,1, {species: 'maple'})])

t.remove(points, 'species', 'dogwood', function(err, result) {
  if(err) throw err
  console.log(result)
})

###filter

Keeps any features from a feature collection that match a property value.

var t = require('turf')
var trees = t.featurecollection([
  t.point(1,2, {species: 'oak'}),
  t.point(2,1, {species: 'birch'}),
  t.point(3,1, {species: 'oak'}),
  t.point(2,2, {species: 'redwood'}),
  t.point(2,3, {species: 'maple'}),
  t.point(4,2, {species: 'oak'})
  ])

t.filter(trees, 'species', 'oak', function(err, oaks){
  if(err) throw err
  console.log(oaks)
})

###inside

Checks to see if a point is inside of a polygon. The polygon can be convex or concave.

var t = require('turf')
var poly = t.polygon([[[0,0], [50, 50], [0,100], [100,100], [100,0]]])
var pt = t.point(75, 75)

t.inside(pt, poly, function(err, isInside){
  if(err) throw err
  console.log(isInside) // true
})

###within

Returns a feature collection of points representing all points that fall withing a collection of polygons.

var t = require('turf')
var poly = t.polygon([[[10,0],[20,10],[20,20], [20,0]]])
var polyFC = t.featurecollection([poly])
var pt1 = t.point(1,1, {population: 500})
var pt2 = t.point(1,3, {population: 400})
var pt3 = t.point(14,2, {population: 600})
var pt4 = t.point(13,1, {population: 500})
var pt5 = t.point(19,7, {population: 200})
var ptFC = t.featurecollection([pt1, pt2, pt3, pt4, pt5])

t.within(ptFC, polyFC, function(err, ptsWithin){
  console.log(ptsWithin) // feature collection with 3 pts
})

###buffer

Buffers a point, linestring, or polygon feature to a given radius. Units supported are miles, kilometers, and degrees.

var t = require('turf')
var pt = t.point(0, 0.5)
var unit = 'miles'

t.buffer(pt, 10, unit, function(err, buffered){
  if(err) throw err
  console.log(buffered)
})

###distance

Calculates the distance between two point features in degrees, radians, miles, or kilometers. This uses the haversine formula to account for global curvature.

var t = require('turf')
var point1 = t.point(-75.343, 39.984)
var point2 = t.point(-75.534, 39.123)
var unit = 'miles' // or 'kilometers', 'degrees', 'radians'

t.distance(point1, point2, unit, function(err, distance){
  if(err) throw err
  console.log(distance)
})

###nearest

Returns the nearest point feature.

var t = require('turf')
var inPoint = t.point(-75.4, 39.4, {name: 'Location A'})

var pt1 = t.point(-75.343, 39.984, {name: 'Location B'})
var pt2 = t.point(-75.833, 39.284, {name: 'Location C'})
var pt3 = t.point(-75.534, 39.123, {name: 'Location D'})
var inFeatures = t.featurecollection([pt1, pt2, pt3])

t.nearest(inPoint, inFeatures, function(err, closestPoint){
  if(err) throw err
  console.log(closestPoint)
})

###tin

Takes a set of points and the name of a z-value property and creates a tin (Triangulated Irregular Network). These are often used for developing elevation contour maps or stepped heat visualizations.

var t = require('turf')
var z = 'elevation'

t.load('/path/to/pointsfeatures/elevationPoints.geojson', function(err, points){
  t.tin(points, z, function(err, tin){
    if(err) throw err
    console.log(tin)
  })
})

###grid

Takes a bounding box and a cell depth and outputs a feature collection of points in a grid.

var t = require('turf')
var depth = 15

t.grid([0,0,10,10], depth, function(err, grid){
  console.log(grid) // 15x15 grid of points in a FeatureCollection
})

###planepoint

Takes a trianglular plane and calculates the z value for a point on the plane.

var t = require('turf')
var point = t.point(-75.3221, 39.529)
// triangle is a polygon with "a", "b", and "c" values representing
// the values of the coordinates in order.
var triangle = t.polygon(
    [[[-75.1221,39.57],[-75.58,39.18],[-75.97,39.86]]],
    {"a": 11, "b": 122, "c": 44}
  )

t.planepoint(point, triangle, function(err, zValue){
  if(err) throw err
  console.log(zValue)
})

###midpoint

Takes two point features and returns the mid point.

var t = require('turf')
var pt1 = t.point(0,0)
var pt2 = t.point(10, 0)

t.midpoint(pt1, pt2, function(err, midpoint){
  if(err) throw err
  console.log(midpoint)
})

###quantile

Takes a set of features, a property name, and a set of percentiles and outputs a quantile array. This can be passed as a break array to the isolines function or the isobands function.

var t = require('turf')
var propertyName = 'elevation'
var percentiles = [10,30,40,60,80,90,99]

t.load('./testIn/Points3.geojson', function(err, pts){
  if(err) throw err
  t.quantile(pts, propertyName, percentiles, function(err, quantiles){
    if(err) throw err
    console.log(quantiles) // [ 12, 25, 29, 52, 76, 99, 143 ]
  })
})

###jenks

Takes a set of features, a property name, and the desired number of breaks and outputs an array of natural breaks. This classification can be used in the isolines function or the isobands function, or for theming.

var t = require('turf')
var propertyName = 'elevation'
var num = 10

t.load('./testIn/Points3.geojson', function(err, pts){
  if(err) throw err
  t.jenks(pts, 'elevation', num, function(err, breaks){
    if(err) throw err
    done() // [ 11, 12, 18, 25, 29, 41, 50, 55, 76, 90, 143 ]
  })
})

###reclass

Takes a feature collection, a in field, an out field, and an array of translations and outputs an identical feature collection with the out field property populated.

var t = require('turf')
var inField = 'elevation',
    outField = 'heightIndex',
    // 0 to 20 will map to 1, 20 to 40 will map to 2, etc.
    translations = [[0, 20, 1], [20, 40, 2], [40, 60 , 3], [60, Infinity, 4]]

t.load('./testIn/Points3.geojson', function(err, pts){
  if(err) throw err
  t.reclass(pts, inField, outField, translations, function(err, outPts){
    if(err) throw err
    console.log(outPts)
  })
})

###contour [deprecated: split into isolines for line contours and isobands for polygon filled contours]

Takes a FeatureCollection of points with z values and an array of value breaks and generates contour polygons. This is a great way to visualize interpolated density on a map. It is often used for elevation maps, weather maps, and isocrones. The main advantage over a heat map is that contours allow you to see definitive value boundaries, and the polygons can be used to aggregate data. For example, you could get the 5000 ft elevation contour of a mountain and the 10000 ft elevation contour, then aggregate the number of trees in each to see how elevation affects tree survival.

var t = require('turf')
var z = 'elevation'
var resolution = 15
var breaks = [.1, 22, 45, 55, 65, 85,  95, 105, 120, 180]
var donuts = false

t.load('../path/to/points.geojson', function(err, points){
  t.contour(points, z, resolution, breaks, donuts, function(err, contours){
    if(err) throw err
    console.log(contours)
  })
})

###isolines

Takes a FeatureCollection of points with z values and an array of value breaks and generates contour isolines. These are commonly used to create elevation maps, but can be used for general data interpolation as well.

var t = require('turf')
var z = 'elevation'
var resolution = 15
var breaks = [.1, 22, 45, 55, 65, 85,  95, 105, 120, 180]

t.load('../path/to/points.geojson', function(err, points){
  t.isolines(points, z, resolution, breaks, function(err, contours){
    if(err) throw err
    console.log(isolines)
  })
})

###isobands

Takes a FeatureCollection of points with z values and an array of value breaks and generates filled contour isobands. These are commonly used to create elevation maps, but can be used for general data interpolation as well.

var t = require('turf')
var z = 'elevation'
var resolution = 15
var breaks = [.1, 22, 45, 55, 65, 85,  95, 105, 120, 180]

t.load('../path/to/points.geojson', function(err, points){
  t.isobands(points, z, resolution, breaks, function(err, contours){
    if(err) throw err
    console.log(isolines)
  })
})

###sample

Takes a feature collection and returns N random features as a feature collection.

var t = require('turf')
var num = 10

t.load('./testIn/Points3.geojson', function(err, pts){
  if(err) throw err
  t.sample(pts, num, function(err, outPts){
    if(err) throw err
    console.log(outPts)
  })
})

###tag

Performs a spatial join on a set of points from a set of polygons.

var t = require('turf')

t.load('./testIn/tagPoints.geojson', function(err, points){
  t.load('./testIn/tagPolygons.geojson', function(err, polygons){
    t.tag(points, polygons, 'polyID', 'containingPolyID', function(err, taggedPoints){
      console.log(taggedPoints)
    })
  })
})

###bezier

Takes a linestring and outputs a curved version of the line.

var t = require('turf')
var resolution = 5000
var intensity = .85
var lineIn = t.linestring([
      [
        -80.08724212646484,
        32.77428536643231
      ],
      [
        -80.03746032714844,
        32.84007757059952
      ],
      [
        -80.01548767089844,
        32.74512501406368
      ],
      [
        -79.95368957519531,
        32.850461360442424
      ]
    ])

t.bezier(lineIn, 5000, .85, function(err, lineOut){
  if(err) throw err
  console.log(lineOut)
})

###simplify

Takes a feature collection of polygons or linestrings and returns a simplified version, preserving topology of shared boundaries.

var t = require('turf')
var quantization = 50
var minimumArea = 0

t.load('./path/to/complex.geojson', function(err, polys){
  t.simplify(polys, quantization, minimumArea, function(err, simplified){
    if(err) throw err
    console.log(simplified)
  })
})

###average

Calculates the average value of a field for points within a set of polygons.

var t = require('turf')

var poly1 = t.polygon([[[0,0],[10,0],[10,10], [0,10]]])
var poly2 = t.polygon([[[10,0],[20,10],[20,20], [20,0]]])
var polyFC = t.featurecollection([poly1, poly2])
var pt1 = t.point(5,5, {population: 200})
var pt2 = t.point(1,3, {population: 600})
var pt3 = t.point(14,2, {population: 100})
var pt4 = t.point(13,1, {population: 200})
var pt5 = t.point(19,7, {population: 300})
var ptFC = t.featurecollection([pt1, pt2, pt3, pt4, pt5])

t.average(polyFC, ptFC, 'population', 'pop_avg', function(err, averaged){
  if(err) throw err

  console.log(averaged.features[0].properties.pop_avg) // 400
  console.log(averaged.features[1].properties.pop_avg) // 200
})

###median

Calculates the median value of a field for points within a set of polygons.

var t = require('turf')

var poly1 = t.polygon([[[0,0],[10,0],[10,10], [0,10]]])
var poly2 = t.polygon([[[10,0],[20,10],[20,20], [20,0]]])
var polyFC = t.featurecollection([poly1, poly2])
var pt1 = t.point(5,5, {population: 200})
var pt2 = t.point(1,3, {population: 600})
var pt3 = t.point(14,2, {population: 100})
var pt4 = t.point(13,1, {population: 200})
var pt5 = t.point(19,7, {population: 300})
var ptFC = t.featurecollection([pt1, pt2, pt3, pt4, pt5])

t.median(polyFC, ptFC, 'population', 'pop_median', function(err, medianed){
  if(err) throw err

  console.log(medianed.features[0].properties.pop_median) // 400
  console.log(medianed.features[1].properties.pop_median) // 200
})

###sum

Calculates the sum value of a field for points within a set of polygons.

var t = require('turf')

var poly1 = t.polygon([[[0,0],[10,0],[10,10], [0,10]]])
var poly2 = t.polygon([[[10,0],[20,10],[20,20], [20,0]]])
var polyFC = t.featurecollection([poly1, poly2])
var pt1 = t.point(1,1, {population: 500})
var pt2 = t.point(1,3, {population: 400})
var pt3 = t.point(14,2, {population: 600})
var pt4 = t.point(13,1, {population: 500})
var pt5 = t.point(19,7, {population: 200})
var ptFC = t.featurecollection([pt1, pt2, pt3, pt4, pt5])

t.sum(polyFC, ptFC, 'population', 'pop_sum', function(err, summed){
  if(err) throw err

  console.log(summed.features[0].properties.pop_sum) // 900
  console.log(summed.features[1].properties.pop_sum) // 1300
})

###min

Calculates the min value of a field for points within a set of polygons.

var t = require('turf')

var poly1 = t.polygon([[[0,0],[10,0],[10,10], [0,10]]])
var poly2 = t.polygon([[[10,0],[20,10],[20,20], [20,0]]])
var polyFC = t.featurecollection([poly1, poly2])
var pt1 = t.point(1,1, {population: 500})
var pt2 = t.point(1,3, {population: 400})
var pt3 = t.point(14,2, {population: 600})
var pt4 = t.point(13,1, {population: 500})
var pt5 = t.point(19,7, {population: 200})
var ptFC = t.featurecollection([pt1, pt2, pt3, pt4, pt5])

t.min(polyFC, ptFC, 'population', 'pop_min', function(err, minPolys){
  if(err) throw err

  console.log(minPolys.features[0].properties.pop_min) // 400
  console.log(minPolys.features[1].properties.pop_min) // 200
})

###max

Calculates the min value of a field for points within a set of polygons.

var t = require('turf')

var poly1 = t.polygon([[[0,0],[10,0],[10,10], [0,10]]])
var poly2 = t.polygon([[[10,0],[20,10],[20,20], [20,0]]])
var polyFC = t.featurecollection([poly1, poly2])
var pt1 = t.point(1,1, {population: 500})
var pt2 = t.point(1,3, {population: 400})
var pt3 = t.point(14,2, {population: 600})
var pt4 = t.point(13,1, {population: 500})
var pt5 = t.point(19,7, {population: 200})
var ptFC = t.featurecollection([pt1, pt2, pt3, pt4, pt5])

t.max(polyFC, ptFC, 'population', 'pop_max', function(err, maxPolys){
  if(err) throw err

  console.log(maxPolys.features[0].properties.pop_max) // 500
  console.log(maxPolys.features[1].properties.pop_max) // 600
})

###count

Calculates the count of points within a set of polygons.

var t = require('turf')

var poly1 = t.polygon([[[0,0],[10,0],[10,10], [0,10]]])
var poly2 = t.polygon([[[10,0],[20,10],[20,20], [20,0]]])
var polyFC = t.featurecollection([poly1, poly2])
var pt1 = t.point(1,1, {population: 500})
var pt2 = t.point(1,3, {population: 400})
var pt3 = t.point(14,2, {population: 600})
var pt4 = t.point(13,1, {population: 500})
var pt5 = t.point(19,7, {population: 200})
var ptFC = t.featurecollection([pt1, pt2, pt3, pt4, pt5])

t.count(polyFC, ptFC, 'population', 'point_count', function(err, counted){
  if(err) throw err

  console.log(counted.features[0].properties.point_count) // 2
  console.log(counted.features[1].properties.point_count) // 3
})

###deviation

Calculates the standard deviation value of a field for points within a set of polygons.

var t = require('turf')

var poly1 = t.polygon([[[0,0],[10,0],[10,10], [0,10]]])
var poly2 = t.polygon([[[10,0],[20,10],[20,20], [20,0]]])
var polyFC = t.featurecollection([poly1, poly2])
var pt1 = t.point(1,1, {population: 500})
var pt2 = t.point(1,3, {population: 400})
var pt3 = t.point(14,2, {population: 600})
var pt4 = t.point(13,1, {population: 500})
var pt5 = t.point(19,7, {population: 200})
var ptFC = t.featurecollection([pt1, pt2, pt3, pt4, pt5])

t.deviation(polyFC, ptFC, 'population', 'pop_deviation', function(err, deviated){
  if(err) throw err

  console.log(deviated.features[0].properties.pop_deviation)
  console.log(deviated.features[1].properties.pop_deviation)
})

###variance

Calculates the standard deviation value of a field for points within a set of polygons.

var t = require('turf')

var poly1 = t.polygon([[[0,0],[10,0],[10,10], [0,10]]])
var poly2 = t.polygon([[[10,0],[20,10],[20,20], [20,0]]])
var polyFC = t.featurecollection([poly1, poly2])
var pt1 = t.point(1,1, {population: 500})
var pt2 = t.point(1,3, {population: 400})
var pt3 = t.point(14,2, {population: 600})
var pt4 = t.point(13,1, {population: 500})
var pt5 = t.point(19,7, {population: 200})
var ptFC = t.featurecollection([pt1, pt2, pt3, pt4, pt5])

t.variance(polyFC, ptFC, 'population', 'pop_variance', function(err, varianced){
  if(err) throw err

  console.log(varianced.features[0].properties.pop_variance)
  console.log(varianced.features[1].properties.pop_variance)
})

###aggregate

Takes a set of polygons, a set of points, and an array of aggregations, then perform them. Sum, average, count, min, max, and deviation are supported.

var t = require('turf')

var poly1 = t.polygon([[[0,0],[10,0],[10,10],[0,10]]])
var poly2 = t.polygon([[[10,0],[20,10],[20,20], [20,0]]])
var polyFC = t.featurecollection([poly1, poly2])
var pt1 = t.point(5,5, {population: 200})
var pt2 = t.point(1,3, {population: 600})
var pt3 = t.point(14,2, {population: 100})
var pt4 = t.point(13,1, {population: 200})
var pt5 = t.point(19,7, {population: 300})
var ptFC = t.featurecollection([pt1, pt2, pt3, pt4, pt5])
var aggregations = [
  {
    aggregation: 'sum',
    inField: 'population',
    outField: 'pop_sum'
  },
  {
    aggregation: 'average',
    inField: 'population',
    outField: 'pop_avg'
  },
  {
    aggregation: 'median',
    inField: 'population',
    outField: 'pop_median'
  },
  {
    aggregation: 'min',
    inField: 'population',
    outField: 'pop_min'
  },
  {
    aggregation: 'max',
    inField: 'population',
    outField: 'pop_max'
  },
  {
    aggregation: 'deviation',
    inField: 'population',
    outField: 'pop_deviation'
  },
  {
    aggregation: 'variance',
    inField: 'population',
    outField: 'pop_variance'
  },
  {
    aggregation: 'count',
    inField: '',
    outField: 'point_count'
  }
]

t.aggregate(polyFC, ptFC, aggregations, function(err, polys){
  if(err) throw err
  console.log(polys)
})

###union

Calculates the union of two polygon features or feature collections.

var t = require('turf')

t.load(__dirname + '/testIn/Intersect1.geojson', function(err, polys1){
  t.load(__dirname + '/testIn/Intersect2.geojson', function(err, polys2){
    t.union(polys1, polys2, function(err, unioned){
      if(err) throw err
      console.log(unioned)
    })
  })
})

###merge

Takes a feature collection of polygons and outputs a single merged polygon feature.

var t = require('turf')

t.load(__dirname + '/testIn/mergeIn.geojson', function(err, polys){
  t.merge(polys, function(err, merged){
    if(err) throw err
    console.log(unioned)
  })
})

###intersect

Calculates the intersection of two polygon features or feature collections.

var t = require('turf')

t.load(__dirname + '/testIn/Intersect1.geojson', function(err, polys1){
  t.load(__dirname + '/testIn/Intersect2.geojson', function(err, polys2){
    t.intersect(polys1, polys2, function(err, intersected){
      if(err) throw err
      console.log(intersected)
    })
  })
})

###erase

Returns polygon 1 minus polygon 2.

var t = require('turf')

t.load(__dirname + '/testIn/Intersect1.geojson', function(err, polys1){
  t.load(__dirname + '/testIn/Intersect2.geojson', function(err, polys2){
    t.erase(polys1, polys2, function(err, erased){
      if(err) throw err
      console.log(erased)
    })
  })
})

###donuts

Takes a set of overlapping polygons and returns non overlapping donuts.

var t = require('turf')

t.load('../path/to/donutsIn.geojson', function(err, donutsIn){
  if(err) throw err
  t.donuts(donutsIn, function(err, donuts){
    if(err) throw err
    console.log(donuts)
  })
})

###convex

Takes a set of points and returns a convex hull polygon.

var t = require('turf')

t.load('../test/testIn/convexIn.geojson', function(err, points){
  t.convex(points, function(err, hull){
    if(err) throw err
    fs.writeFileSync('./testOut/convex.geojson', JSON.stringify(hull))
    console.log(hull)
  })
})

###concave

Takes a set of points and returns a concave hull polygon.

var t = require('turf')
var maxEdge = 2.5

t.load('../test/testIn/concaveIn.geojson', function(err, points){
  t.concave(points, maxEdge, function(err, hull){
    if(err) throw err
    console.log(hull)
  })
})

---

This library is built and maintained by @morganherlocker :)