Deleting close points from FeatureCollection using buffer in Google Earth Engine?

Question

I want to generate a number of random points over a given area, e.g. all land masses of the world. For this I have coded

var fcLandMasses = ee.FeatureCollection('ft:1l9VK5FJ4_hiH2gHjr0MtxwB-CrNEqOE5EBlW6Q');
var fcRandomPoints = ee.FeatureCollection.randomPoints(fcLandMasses,numberOfPoints,seed);

where you need to set numberOfPoints to the number of points you want to generate and seed to an arbitrary non-negative integer to ensure repeatability.

How can I clean up the FeatureCollection fcRandomPoints such that points located too close to each other (i.e. within a certain buffer) are removed?

I think there are two general choices:

1. Keeping one (e.g. the first-appearing) point of points within that buffer.
2. Keeping the average of all points within that buffer.

I'd like to follow option 2, which will probably include a mapping over fcRandomPoints.

What is the most efficient way to implement this?

Answer 1

Option 1 (You can also find it here: https://github.com/gee-community/gee_tools):

var filterDistance = function(points, distance) {
  var filt2 = ee.List([])
  var filt = points.iterate(function(el, ini){
                         var ini = ee.List(ini)
                         var fcini = ee.FeatureCollection(ini)
                         var buf = ee.Feature(el).geometry().buffer(distance)
                         var s = fcini.filterBounds(buf).size()
                         var cond = s.lte(0)
                         return ee.Algorithms.If(cond, ini.add(el), ini)
                       }, filt2)
  var filtered = ee.FeatureCollection(ee.List(filt))
  return filtered
}

Option 2:

var filterDistance = function(points, distance) {      
  var sum = points.iterate(function(el,fir){
    var buf = ee.Feature(el).geometry().buffer(distance)
    var s = points.filterBounds(buf).size()
    return ee.Number(fir).add(s)
  },ee.Number(0))
  var mean = ee.Number(sum).divide(points.size()).ceil()

  var filt2 = ee.List([])
  var filt = points.iterate(function(el, ini){
                         var ini = ee.List(ini)
                         var fcini = ee.FeatureCollection(ini)
                         var buf = ee.Feature(el).geometry().buffer(distance)
                         var s = fcini.filterBounds(buf).size()
                         var cond = s.lte(mean)
                         return ee.Algorithms.If(cond, ini.add(el), ini)
                       }, filt2)
  var filtered = ee.FeatureCollection(ee.List(filt))
  return filtered
}

Test

// TEST
var r1 = filterDistance(fcRandomPoints, 50000)
Map.addLayer(r1)
Map.addLayer(fcRandomPoints)
print(r1.size())

I think option 1 works better (cleaner), but of course depends on your needs.