How does one merge coordinate values of an array of geojson items?

Question

Hello I am working with a large geojson dataset, and I am trying to see if I can merge the coordinate values of each entry based on entries that share the same "User_ID".

My dataset look like this:

{
     "geometry":{
        "type":"Point",
        "coordinates":[
           -3.231658,
           51.687026
        ]
     },
     "type":"Feature",
     "properties":{
        "User_ID":1002848324
     }
  },
  {
     "geometry":{
        "type":"Point",
        "coordinates":[
           -3.231659,
           51.687016
        ]
     },
     "type":"Feature",
     "properties":{
        "User_ID":1002848324
     }
  }

I have tried to merge the entries using the method shown in mwarren's answer, url: "https://stackoverflow.com/questions/29244116/merge-geojson-based-on-unique-id".

Yet this comes with the small problem that "attr" is seen as an "Unexpected Identifier" when I try to run a test.

My test of the code so far is as follows:

features.map(function(feature){
var matchedArray = features2.filter(function(feature2){
    return feature2.User_ID === feature.User_ID;
});
   if(matchedArray && matchedArray[0]){
      for(var attr in matchedArray[0].properties){
          feature.properties[attr] = matchedArray[0].properties[attr];
    }
  }
});

The desired result should look something like this:

{
     "geometry":{
        "type":"Point",
        "coordinates":[
           -3.231658,
           51.687026
        ], [
           -3.231659,
           51.687016
        ]
     },
     "type":"Feature",
     "properties":{
        "User_ID":1002848324
     }

Any help will be greatly appreciated.

Answer 1

You have spelled var to "war" which needs to be 'var'. and if this is not a mistake please specify what is 'features2' array.

Answer 2

From the above comment ...

"The OP needs to group/collect the data not only by same User_ID values but by both same type AND same User_ID values"

... and maybe even by same geometry.type . A just User_ID based grouping/collecting is not explicit enough because items of same User_ID values might feature different type values or might even differ in their geometry.type values.

A reduce based task which uses a collector object which features an object as lookup and an result array for the aggregated final data does solve the OP's task within one iteration step ...

 function collectSameGeoCategoryItems(collector, item) { const { lookup, result } = collector; const { properties: { User_ID }, type } = item; const groupKey = `${ type }_${ User_ID }`; let groupItem = lookup[groupKey]; if (groupItem) { // push coordinates copy into existing array of coordinate arrays. groupItem.geometry.coordinates.push([...item.geometry.coordinates]); } else { // create full copy of geo item in order // to not mutate the original reference. groupItem = lookup[groupKey] = { geometry: { type: item.geometry.type, coordinates: [ [...item.geometry.coordinates] ], }, type, properties: { User_ID }, }; result.push(groupItem); } return collector; } const sampleData = [{ geometry: { type: "Point", coordinates: [ -3.231658, 51.687026, ], }, type: "Feature", properties: { User_ID: 1002848324, }, }, { geometry: { type: "Point", coordinates: [ -3.231659, 51.687016, ], }, type: "Feature", properties: { User_ID: 1002848324, }, }, { geometry: { type: "Point", coordinates: [ -3.231658, 51.687026, ], }, type: "Foo", properties: { User_ID: 1002848324, }, }, { geometry: { type: "Point", coordinates: [ -3.231659, 51.687016, ], }, type: "Bar", properties: { User_ID: 1002848324, }, }, { geometry: { type: "Point", coordinates: [ -3.231658, 51.687026, ], }, type: "Foo", properties: { User_ID: 1000000000, }, }, { geometry: { type: "Point", coordinates: [ -3.231659, 51.687016, ], }, type: "Bar", properties: { User_ID: 1002848324, }, }]; console.log( 'aggregated `result` ...', sampleData.reduce(collectSameGeoCategoryItems, { lookup: {}, result: [] }).result ); console.log('unmutated sample data ... ', { sampleData }); console.log( 'aggregated `lookup`, not needed, just for demonstration purpose ...', sampleData.reduce(collectSameGeoCategoryItems, { lookup: {}, result: [] }).lookup );

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