code: public static int quantile(ArrayModifiableDBIDs data, Comparator<? super DBIDRef> comparator, double quant) {
      return quantile(data, comparator, 0, data.size(), quant);
    }
docs: Compute the median of an array efficiently using the QuickSelect method.
  
  Note: the array is <b>modified</b> by this.
  
  @param data Data to process
  @param comparator Comparator to use
  @param quant Quantile to compute
  @return Quantile position