We Keep Coding

Each LinearRing of a Polygon must have 4 or more Positions with turf.mask() for JavaScript

I am trying to use turf.mask() on these two polygons: state and hexagon.
state = {"type":"Feature","properties":{},"geometry":{"type":"MultiPolygon","coordinates":[[[[-122.5399362859679,37.830838250358305],[-122.5352992,37.8292543],[-122.5360944,37.8239044],[-122.5279709,37.8153353],[-122.5292904,37.8198549],[-122.5229995,37.8251486],[-122.5099818,37.8245382],[-122.4995901,37.8199115],[-122.4907812,37.8266974],[-122.478306,37.8254268],[-122.47823831099781,37.83244271995018],[-122.5399362859679,37.83244271995018],[-122.5399362859679,37.830838250358305]]],[[[-122.5209211,37.5943953],[-122.5172512,37.5892786],[-122.5205505,37.5739919],[-122.5144188,37.5657519],[-122.5135889,37.5559887],[-122.5197357,37.5371873],[-122.5179299,37.5238199],[-122.5118361,37.5131343],[-122.4987459,37.5009924],[-122.4993886,37.4956524],[-122.4934399,37.4929939],[-122.4845619,37.493956],[-122.4933403,37.4931535],[-122.4963325,37.4978499],[-122.4870092,37.5037473],[-122.4837393,37.5005349],[-122.485041,37.5028707],[-122.4795964,37.5033699],[-122.4805619,37.5005397],[-122.4770952,37.5024601],[-122.4745322,37.5006196],[-122.4858172,37.49523],[-122.4706747,37.5007852],[-122.4584325,37.4908973],[-122.4508972389485,37.47800498084561],[-122.2721445405403,37.47800498084561],[-122.2721445405403,37.57062405456298],[-122.2734391,37.5701746],[-122.2845216,37.5757537],[-122.2915515,37.5743495],[-122.2933973,37.5691119],[-122.2968954,37.5755277],[-122.305437,37.5749218],[-122.316048,37.5840024],[-122.3139154,37.5900472],[-122.3165712,37.5867603],[-122.3173273,37.5903678],[-122.3177269,37.5867609],[-122.318293,37.5911926],[-122.3145503,37.5923252],[-122.3325163,37.5877861],[-122.3344629,37.5920779],[-122.3380163,37.5920507],[-122.3384833,37.5871208],[-122.3579245,37.5888057],[-122.3383946,37.5882378],[-122.3384111,37.5919623],[-122.3459053,37.5898998],[-122.3439243,37.5920571],[-122.360012,37.592015],[-122.3640642,37.598455],[-122.3786677,37.6059181],[-122.3713687,37.6147206],[-122.3582017,37.6089833],[-122.3548517,37.6148603],[-122.3681936,37.6210318],[-122.3653327,37.6281401],[-122.3736554,37.6279567],[-122.3789373,37.6315371],[-122.3861757,37.6288252],[-122.3878968,37.634473],[-122.3796783,37.6351943],[-122.3837736,37.6399334],[-122.3911844,37.6391024],[-122.3909661,37.6444244],[-122.3917268,37.6390208],[-122.3965553,37.6388167],[-122.3934705,37.6438287],[-122.3992832,37.642004],[-122.4028452,37.6426094],[-122.4013169,37.6461099],[-122.3994533,37.6431429],[-122.396963,37.6427665],[-122.3917379,37.6477991],[-122.3803373,37.648125],[-122.3755326,37.6549592],[-122.3799605,37.6607485],[-122.3744577,37.6624522],[-122.3829018,37.6631099],[-122.3811718,37.6681459],[-122.3859696,37.667591],[-122.3869568,37.6645382],[-122.3952727,37.6650535],[-122.3874281,37.6716869],[-122.3810763,37.6718878],[-122.3811199,37.6773246],[-122.3878163,37.6783848],[-122.3941205,37.7073575],[-122.3914199,37.7096391],[-122.3744129,37.7086766],[-122.3800854,37.7106027],[-122.3759862,37.7160655],[-122.3869772,37.7242593],[-122.3808547,37.7217156],[-122.3768873,37.7239002],[-122.3738477,37.7188103],[-122.3654008,37.7160347],[-122.3627284,37.7200714],[-122.3590965,37.7193159],[-122.3652453,37.7256766],[-122.3577914,37.7246098],[-122.3616456,37.7251817],[-122.3569649,37.728662],[-122.3622605,37.7284968],[-122.3588648,37.7297956],[-122.3658749,37.7331392],[-122.3754819,37.7328043],[-122.3764548,37.739765],[-122.3732029,37.7372296],[-122.3675347,37.7382209],[-122.3735546,37.7386854],[-122.3676515,37.740137],[-122.3752341,37.7468542],[-122.3929128,37.7474166],[-122.3757592,37.7487044],[-122.3761037,37.752267],[-122.3841093,37.7546193],[-122.3808144,37.755204],[-122.3838352,37.7620693],[-122.3810399,37.762589],[-122.3870406,37.7637898],[-122.3856126,37.7702142],[-122.3831784,37.7697199],[-122.3867755,37.7732761],[-122.381492,37.7719454],[-122.381849,37.7746281],[-122.3869477,37.7743538],[-122.3850142,37.776339],[-122.3899459,37.7766762],[-122.398671,37.7705013],[-122.3902987,37.7772108],[-122.3874581,37.7783059],[-122.3877716,37.7822999],[-122.3847049,37.7825645],[-122.3876263,37.7854527],[-122.3845243,37.7873797],[-122.3874381,37.7872449],[-122.3852995,37.7898012],[-122.3976619,37.7998545],[-122.3957218,37.8014672],[-122.3983318,37.8006011],[-122.3971208,37.8030526],[-122.3997229,37.8021723],[-122.3985174,37.8045967],[-122.4009866,37.8035636],[-122.4003819,37.8072585],[-122.4028024,37.8060243],[-122.4043847,37.8088919],[-122.4053268,37.8068875],[-122.4104297,37.811425],[-122.4105114,37.8087706],[-122.4203547,37.8115306],[-122.4163293,37.80833],[-122.4228214,37.8102504],[-122.4210749,37.8085664],[-122.424679,37.8066449],[-122.4301758,37.809232],[-122.4328481,37.8057039],[-122.435879,37.8075603],[-122.4473666,37.8055087],[-122.440031,37.808853],[-122.4632009,37.8050656],[-122.4777987,37.8109716],[-122.4869244,37.789907],[-122.5059955,37.7881687],[-122.5147128,37.7811281],[-122.5070212,37.7235595],[-122.4963102,37.6820786],[-122.4941412,37.6435021],[-122.4960688,37.6232689],[-122.4990205,37.6201788],[-122.4969547,37.6120108],[-122.5020589,37.6067327],[-122.5006007,37.6013344],[-122.5060876,37.5963957],[-122.5149418,37.5987038],[-122.5151511,37.5958341],[-122.5209211,37.5943953]]],[[[-122.47454130078302,37.83244271995018],[-122.4727523,37.8320753],[-122.4726672512427,37.83244271995018],[-122.47454130078302,37.83244271995018]]],[[[-122.379047,37.8267146],[-122.3713678,37.8151916],[-122.3727963,37.8108587],[-122.3619928,37.8070656],[-122.3589024,37.8147697],[-122.3672433,37.8122518],[-122.3704001,37.8142932],[-122.3629308,37.8226056],[-122.3686209,37.8310775],[-122.3733669,37.8322631],[-122.379047,37.8267146]]],[[[-122.3426269,37.8057313],[-122.3413237,37.803655],[-122.3249395,37.8067225],[-122.3252406,37.8000102],[-122.330053,37.799951],[-122.3055583,37.7937247],[-122.2805644,37.7957313],[-122.2721445405403,37.79148781862211],[-122.2721445405403,37.83244271995018],[-122.29662795299252,37.83244271995018],[-122.2950082,37.8292417],[-122.3055254,37.826014],[-122.3148745,37.8257845],[-122.3119885,37.82721],[-122.3160071,37.8278395],[-122.3214924,37.8230959],[-122.3300331,37.8216442],[-122.3188547,37.8187413],[-122.3151503,37.8218637],[-122.3083022,37.8210817],[-122.322915,37.8101466],[-122.3330683,37.8110303],[-122.3426269,37.8057313]]],[[[-122.3316381,37.7814097],[-122.3075012,37.7760617],[-122.3082387,37.7803977],[-122.298304,37.7800123],[-122.3011353,37.7742605],[-122.2914341,37.7681259],[-122.2815741,37.7711087],[-122.280682,37.7662999],[-122.276538,37.768255],[-122.2721445405403,37.76325713296079],[-122.2721445405403,37.78664847083194],[-122.2783834,37.7918049],[-122.3005534,37.790309],[-122.3314733,37.7968291],[-122.3316381,37.7814097]]],[[[-122.2887255,37.7656186],[-122.2827173,37.763773],[-122.2871204,37.7658696],[-122.2842014,37.7673989],[-122.2860548,37.7695738],[-122.2887255,37.7656186]]]]}}
hex = {"type":"Feature","properties":{},"geometry":{"type":"MultiPolygon","coordinates":[[[[-121.91508032705622,37.271355866731895],[-121.86222328902491,37.353926450852256],[-121.92354999630157,37.42834118609435],[-122.03773496427027,37.42012867767778],[-122.09042892904397,37.33755608435298],[-122.02910130918998,37.26319797461824],[-121.91508032705622,37.271355866731895]]],[[[-122.09042892904397,37.33755608435298],[-122.03773496427027,37.42012867767778],[-122.0991572595036,37.49436145881944],[-122.21327339445754,37.485965058551095],[-122.2658032483195,37.4033911145053],[-122.20438138645652,37.32921488696578],[-122.09042892904397,37.33755608435298]]],[[[-122.2658032483195,37.4033911145053],[-122.21327339445754,37.485965058551095],[-122.27479015180235,37.560015298456165],[-122.38883528966466,37.551435083769555],[-122.44120000376466,37.46886044817503],[-122.37968502627967,37.39486668388987],[-122.2658032483195,37.4033911145053]]],[[[-122.27479015180235,37.560015298456165],[-122.2221915863209,37.64251820979243],[-122.28380352912619,37.71644156150208],[-122.39801249019256,37.707805739822945],[-122.45044537747678,37.625302208372474],[-122.38883528966466,37.551435083769555],[-122.27479015180235,37.560015298456165]]],[[[-122.44120000376466,37.46886044817503],[-122.38883528966466,37.551435083769555],[-122.45044537747678,37.625302208372474],[-122.56441735732743,37.61653827043709],[-122.61661591173977,37.53396360310495],[-122.55500895066726,37.46015287008624],[-122.44120000376466,37.46886044817503]]],[[[-122.45044537747678,37.625302208372474],[-122.39801249019256,37.707805739822945],[-122.4597179789842,37.781545330604914],[-122.57385345315238,37.77272521206777],[-122.62611963828853,37.69022171873274],[-122.56441735732743,37.61653827043709],[-122.45044537747678,37.625302208372474]]],[[[-122.28380352912619,37.71644156150208],[-122.23113607743653,37.79887236738518],[-122.29284349699644,37.872667939497596],[-122.4072167465147,37.863976689425115],[-122.4597179789842,37.781545330604914],[-122.39801249019256,37.707805739822945],[-122.28380352912619,37.71644156150208]]],[[[-122.28380352912619,37.71644156150208],[-122.23113607743653,37.79887236738518],[-122.29284349699644,37.872667939497596],[-122.4072167465147,37.863976689425115],[-122.4597179789842,37.781545330604914],[-122.39801249019256,37.707805739822945],[-122.28380352912619,37.71644156150208]]],[[[-122.28380352912619,37.71644156150208],[-122.23113607743653,37.79887236738518],[-122.29284349699644,37.872667939497596],[-122.4072167465147,37.863976689425115],[-122.4597179789842,37.781545330604914],[-122.39801249019256,37.707805739822945],[-122.28380352912619,37.71644156150208]]],[[[-122.28380352912619,37.71644156150208],[-122.23113607743653,37.79887236738518],[-122.29284349699644,37.872667939497596],[-122.4072167465147,37.863976689425115],[-122.4597179789842,37.781545330604914],[-122.39801249019256,37.707805739822945],[-122.28380352912619,37.71644156150208]]],[[[-122.28380352912619,37.71644156150208],[-122.23113607743653,37.79887236738518],[-122.29284349699644,37.872667939497596],[-122.4072167465147,37.863976689425115],[-122.4597179789842,37.781545330604914],[-122.39801249019256,37.707805739822945],[-122.28380352912619,37.71644156150208]]],[[[-122.28380352912619,37.71644156150208],[-122.23113607743653,37.79887236738518],[-122.29284349699644,37.872667939497596],[-122.4072167465147,37.863976689425115],[-122.4597179789842,37.781545330604914],[-122.39801249019256,37.707805739822945],[-122.28380352912619,37.71644156150208]]],[[[-122.28380352912619,37.71644156150208],[-122.23113607743653,37.79887236738518],[-122.29284349699644,37.872667939497596],[-122.4072167465147,37.863976689425115],[-122.4597179789842,37.781545330604914],[-122.39801249019256,37.707805739822945],[-122.28380352912619,37.71644156150208]]]]}}
I can visualize them on geojson.io. They are correctly visualized there.
However, when I try to run
mask(hex, state);
I am getting
Each LinearRing of a Polygon must have 4 or more Positions.
Which I do not understand.... Why can't it mask the polygon?

One cannot use two multipolygons with turf.mask(). The first argument of turf.mask() can be a polygon or multipolygon. But the second argument must be a polygon, not a multipolygon!

When cutting a polygon with a polyline the geometry engine will group certain peices together?? Arcgis javascript api

When preforming a cut action on a polygon with a polyline, some of the returned geometries are grouped while others are not?
I have a simple program where the user can create a polygon with a SketchViewModel. Then the user creates a polyline with a SketchViewModel. I then take the geometry from each sketch and preform a cut from the geometryEngine. I get an array of geometries from the cut and add them to the layer while removing the original polygon and polyline. I would expect to get each subdivided piece individually but for some reason some get grouped together as one geometry even if they're not connected.
//polylineLayer and polygonLayer are graphiclayers
//submit is a html button to call the execution
submit.addEventListener("click", function() {
//subDivisions is an Geometry[] for the produced geometries
//ex. one line through a circle polygon would produce
// two geometries of each half. (this works)
// anything more complicated starts having grouping issues
// (see pictures)
var subDivisions =
geometryEngine.cut(polygonLayer.graphics.getItemAt(0).geometry,
polylineLayer.graphics.getItemAt(0).geometry);
polygonLayer.removeAll();
polylineLayer.removeAll();
//show the number of subdivisions
alert("size: " + subDivisions.length);
// add created geometries to the graphiclayer
for (var i = 0; i < subDivisions.length; i++){
tempGraphic = new Graphic ({
geometry: subDivisions[i]
});
polygonLayer.graphics.add(tempGraphic,i);
}
});
(sorry for the links to photos I don't have 10 reputation to post photos and this is a very visual project/issue)
Open screen:
https://ibb.co/WDcgmSn
Draw first polygon:
https://ibb.co/wd6CDbV
Draw polyline to cut polygon:
https://ibb.co/BG32863
Expected subdivisions - 10 Actual - 7:
https://ibb.co/0VMsHGg
Some are split into individual polygons:
https://ibb.co/SKXCJR8
Others are not:
https://ibb.co/7WqNB9q
All broken up pieces:
https://ibb.co/Pr0smrw

Wish I could comment instead of just answer but hard to say with out code.
Basically you are getting multipart polygons, you need to break those up.
Use a split in your array to break up the multi-part polygons split("]],[[")
Simplify Polygons using a geometry service would be worth a shot too. (before and after cutting)
https://developers.arcgis.com/rest/services-reference/geometry-service.htm

How to get L.polygon border, excluding inner points

I am working with Leaflet.js library. I have an array of geographical points, described by latitude and longitude and a polygon, based on this points. How can i remove inner points of polygon and draw only it's outer border?
Array of points
[[53, 31], [51.4, 31.2], [51.3, 32] ... etc.] //it's length ~ 500 points.
Initializing map
L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png').addTo(mymap);
Setting polygon
L.polygon(points, {color: 'red'}).addTo(mymap);
This is what i have right now. Here is all of 500 points is shown.
Result i am expecting. Here all internal points are removed, showing the covered area.

Sounds like you are looking for a convex hull algorithm: it would provide you with the "envelope" of your Points.
You can use e.g. Turfjs: https://turfjs.org/docs/#convex
But note that it requires working with data converted to GeoJSON objects.
You can also have a look at how Leaflet.markercluster plugin has implemented it.

Excluding last element of array with slice

In an application I am working with arrays of coordinates - when I log the points of feature to the console, I am returned an array of 5 coordinate pairs:
var poly = data.features[0].geometry.coordinates
console.log(poly)
However, when I use slice() to exclude the last element of the array - which should return 4 instead of 5 - I am returned a blank array
var poly = data.features[0].geometry.coordinates.slice(0, -1);
console.log(poly)
Why does this happen and why doesn't the slice() method work in this case?

Poly is an array with a single element, what you really want is
var poly = data.features[0].geometry.coordinates[0].slice(0, -1);

It looks like you are using GeoJSON data and you want to strip off the duplicate coordinate at the end of a ring. This being the case, you should be aware that your coordinates array (the one with a single element that has the array of points inside it) may actually contain more than one element. In GeoJSON, a polygon is not the same concept as in geometry. A geographic "polygon" consists of an outer "ring" and zero or more inner rings. A "ring" is like a polygon in geometry.
The first ring in a polygon - the single ring that your example has - is the "outer ring", that is the outer boundary of the area you're mapping. Any additional rings are "inner rings" which represent holes that are excluded from the area. For example, a state or county with two lakes in it might be represent as a polygon with three rings, one for the outer boundary and the other two for each of the lakes.
Also, are you checking geometry.type before assuming that geometry.coordinates is a Polygon at all? You may unexpectedly receive a MultiPolygon, which is an array of polygons, so now you have one more level of nested arrays. GeoJSON data sources will often use either a Polygon or MultiPolygon as needed.
Consider the state of Utah. It has a single outer boundary, and of course has the Great Salt Lake inside it (along with some smaller lakes). So Utah can be represented by a Polygon with outer ring for the state border and inner rings for the Great Salt Lake and other lakes.
But what about Hawaii? It consists of several islands. There is no single outer boundary for the state. Each island requires its own outer boundary. So Hawaii has to be represented by a MultiPolygon, i.e. an array of Polygon arrays. Each island gets its own Polygon.
Whatever code you're writing, it should take all this into account. You should distinguish between a Polygon and a MultiPolygon and for the latter, process each Polygon that makes up the MultiPolygon. And if you're stripping off the last element from each polygon's outer ring, you probably want to do that for the inner rings as well. For more details, see the GeoJSON RFC.
I would provide some sample code to do all this, but I'm not clear enough on what you're working toward. But this should at least give you some direction.

As you can see on your screenshot,
var poly = data.features[0].geometry.coordinates
returns [Array(5)] which is essentially a two dimensional array. To exclude the last element in the nested array, you'll need to do
// coordinates[0] returns the first item in the array which is Array(5)
var poly = data.features[0].geometry.coordinates[0].slice(0, -1);
To keep a two dimensional array minus the last coordinate pair instead, you need to recursively clone each element.
var poly = data.features[0].geometry.coordinates.map(function(val) {
return val.slice(0, -1);
});

Leaflet.js - Fit geoJSON co-ordinates on map view

I have a leaflet.js map that has points and linestrings on it that come from an external JSON file.
If I add:
map.setView(new L.LatLng(0,0), 10);
It will centre the map on the latitude and longitude 0,0. How can I set it so the map centre and zoom fit all of the points from the JSON on it?

You could add all of your layers to a FeatureGroup which has a getBounds method. So you should be able to just say myMap.fitBounds(myFeatureGroup.getBounds());
The getBounds method for L.FeatureGroup is only available in the master branch (not the latest version, 0.3.1), for now at least.

Similar case with me. I drawn all the markers from GeoJson data. So I written the function, which gets called repeatedly on button click. Just try if it suits your requirements.
function bestFitZoom()
{
// declaring the group variable
var group = new L.featureGroup;
// map._layers gives all the layers of the map including main container
// so looping in all those layers filtering those having feature
$.each(map._layers, function(ml){
// here we can be more specific to feature for point, line etc.
if(map._layers[].feature)
{
group.addLayer(this)
}
})
map.fitBounds(group.getBounds());
}
The best use of writing this function is that even state of map/markers changed, it will get latest/current state of markers/layers. Whenever this method gets called all the layers will be visible to modest zoom level.

I needed to do this when showing a user directions from his origin to a destination. I store my list of directions in an array of L.LatLng called directionLatLngs then you can simply call
map.fitBounds(directionLatLngs);
This works because map.fitBounds takes a L.LatLngBounds object which is just an array of L.LatLng
http://leafletjs.com/reference.html#latlngbounds