text: import "../math/number";
  import "ascending";
  import "quantile";
  
  d3.median = function(array, f) {
    if (arguments.length > 1) array = array.map(f);
    array = array.filter(d3_number);
    return array.length ? d3.quantile(array.sort(d3.ascending), .5) : undefined;
  };
  