headtail.js

function headTails(arr){

  var breaks = [],
      avg = mean(arr),
      head = arr.filter(function(d){
        return d > avg;
      });
  
  while (head.length && head.length < Math.floor(arr.length/2)) {

    breaks.push(avg);
    arr = head;
    avg = mean(arr);
    head = arr.filter(function(d){
      return d > avg;
    });

  }
  
  return breaks;

}

function mean(a){
  var total = a.reduce(function(p, v){ return p + v}, 0);
  return total/a.length;
}