Function stackNormalize

docs/tests/v2/es6/js/sanddance.js:111319–111332

(group, max, field, y0, y1)

}

function stackNormalize(group, max, field, y0, y1) {
  var scale = 1 / group.sum,
      last = 0,
      m = group.length,
      j = 0,
      v = 0,
      t;

  for (; j < m; ++j) {
    t = group[j];
    t[y0] = last;
    t[y1] = last = scale * (v += Math.abs(field(t)));
  }
}

function stackZero(group, max, field, y0, y1) {
  var lastPos = 0,