d3.zip = function() {

  if (!(n = arguments.length)) return [];

  for (var i = -1, m = d3.min(arguments, d3_zipLength), zips = new Array(m); ++i < m;) {

    for (var j = -1, n, zip = zips[i] = new Array(n); ++j < n;) {

      zip[j] = arguments[j][i];

    }

  }

  return zips;

};

function d3_zipLength(d) {

  return d.length;

}