partition set of numbers into subsets of equal size

equibin.scala

def equibin(a:Seq[Double], depth:Int) = {    
  val d = a.size/depth
  (0 until a.size) // ordered set of indexes of all values
  .groupBy(i=>i/d).values.toList.sortBy(s=>s(0)) // split set into 'd' separate lists
  .map { group => group.map( i => a(i) ) } // map onto value set
  .map { values => ( (min(a),max(a)), values ) }// each bin gets min-max metadata
}