function randomPoints(_num, _dist, _xR, _yR) {
  if(arguments.length<2) _dist = 'irwinHall'
  if(!_xR||!_yR) {
    var xRange = yRange = [0,1]
  }else{
    var xRange = d3.range(_xR[0],_xR[1])
    var yRange = d3.range(_yR[0],_yR[1])
  }

  if(_dist == 'uniform'){
    x = d3.range(0,_num).map(function () {
        return d3.shuffle(xRange)[0]
    })
    y = d3.range(0,_num).map(function () {
        return d3.shuffle(yRange)[0]
    })
  }else{
    x = d3.range(0,_num).map(function () {
        if(['bates','irwinHall'].indexOf(_dist)>-1){
          rnd = d3.random[_dist](_dist=='bates'?8:1)()
          rnd = Math.round(rnd*d3.max(xRange))
        }else if(_dist=='normal'){
          rnd = d3.random[_dist](d3.mean(xRange),d3.mean(xRange)/6)()
        }else if(_dist=='logNormal'){
          rnd = d3.random[_dist]()()
          rnd = Math.round(rnd*d3.mean(xRange)/6)
        }
        return rnd
    }).map(function (d) {return Math.abs(d)})
    y = d3.range(0,_num).map(function () {
        if(['bates','irwinHall'].indexOf(_dist)>-1){
          rnd = d3.random[_dist](_dist=='bates'?8:1)()
          rnd = Math.round(rnd*d3.max(yRange))
        }else if(_dist=='normal'){
          rnd = d3.random[_dist](d3.mean(yRange),d3.mean(yRange)/6)()
        }else if(_dist=='logNormal'){
          rnd = d3.random[_dist]()()
          rnd = Math.round(rnd*d3.mean(yRange)/6)
        }
        return rnd
    }).map(function (d) {return Math.abs(d)})
  }
  return  d3.zip(x,y).map(function(d){return {x:d[0],y:d[1]}})
}
function clusterPoints(numC,numPts,_dist,_xR,_yR){
  var clusters = []
  d3.range(0,numC).forEach(function (i) {
    cPts = randomPoints(4,'uniform',_xR,_yR)
    c={}
    c.dist = _dist
    c.xRange = d3.extent(cPts.map(function(p){return p.x}))
    c.yRange = d3.extent(cPts.map(function(p){return p.y}))
    c.points = randomPoints(numPts,c.dist,c.xRange,c.yRange)
    clusters.push(c)
  })
  // clusters.reduce(function (prev,curr) {return prev.concat(curr)})
  return clusters
}