| 1 | var each = require('turf-meta').coordEach,
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| 2 | convexHull = require('convex-hull'),
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| 3 | polygon = require('turf-helpers').polygon;
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| 4 |
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| 5 | /**
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| 6 | * Takes a set of {@link Point|points} and returns a
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| 7 | * [convex hull](http://en.wikipedia.org/wiki/Convex_hull) polygon.
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| 8 | *
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| 9 | * Internally this uses
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| 10 | * the [convex-hull](https://github.com/mikolalysenko/convex-hull) module that
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| 11 | * implements a [monotone chain hull](http://en.wikibooks.org/wiki/Algorithm_Implementation/Geometry/Convex_hull/Monotone_chain).
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| 12 | *
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| 13 | * @name convex
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| 14 | * @param {FeatureCollection<Point>} input input points
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| 15 | * @returns {Feature<Polygon>} a convex hull
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| 16 | * @example
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| 17 | * var points = {
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| 18 | * "type": "FeatureCollection",
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| 19 | * "features": [
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| 20 | * {
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| 21 | * "type": "Feature",
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| 22 | * "properties": {},
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| 23 | * "geometry": {
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| 24 | * "type": "Point",
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| 25 | * "coordinates": [10.195312, 43.755225]
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| 26 | * }
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| 27 | * }, {
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| 28 | * "type": "Feature",
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| 29 | * "properties": {},
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| 30 | * "geometry": {
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| 31 | * "type": "Point",
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| 32 | * "coordinates": [10.404052, 43.8424511]
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| 33 | * }
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| 34 | * }, {
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| 35 | * "type": "Feature",
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| 36 | * "properties": {},
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| 37 | * "geometry": {
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| 38 | * "type": "Point",
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| 39 | * "coordinates": [10.579833, 43.659924]
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| 40 | * }
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| 41 | * }, {
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| 42 | * "type": "Feature",
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| 43 | * "properties": {},
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| 44 | * "geometry": {
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| 45 | * "type": "Point",
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| 46 | * "coordinates": [10.360107, 43.516688]
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| 47 | * }
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| 48 | * }, {
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| 49 | * "type": "Feature",
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| 50 | * "properties": {},
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| 51 | * "geometry": {
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| 52 | * "type": "Point",
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| 53 | * "coordinates": [10.14038, 43.588348]
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| 54 | * }
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| 55 | * }, {
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| 56 | * "type": "Feature",
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| 57 | * "properties": {},
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| 58 | * "geometry": {
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| 59 | * "type": "Point",
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| 60 | * "coordinates": [10.195312, 43.755225]
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| 61 | * }
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| 62 | * }
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| 63 | * ]
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| 64 | * };
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| 65 | *
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| 66 | * var hull = turf.convex(points);
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| 67 | *
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| 68 | * var resultFeatures = points.features.concat(hull);
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| 69 | * var result = {
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| 70 | * "type": "FeatureCollection",
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| 71 | * "features": resultFeatures
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| 72 | * };
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| 73 | *
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| 74 | * //=result
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| 75 | */
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| 76 | module.exports = function (fc) {
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| 77 | var points = [];
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| 78 | each(fc, function (coord) { points.push(coord); });
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| 79 | var hull = convexHull(points);
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| 80 | if (hull.length > 0) {
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| 81 | var ring = [];
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| 82 | for (var i = 0; i < hull.length; i++) {
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| 83 | ring.push(points[hull[i][0]]);
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| 84 | }
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| 85 | ring.push(points[hull[hull.length - 1][1]]);
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| 86 | return polygon([ring]);
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| 87 | }
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| 88 | return undefined;
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| 89 | };
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