Function stack

external/.d3.js:19381–19423

()

}

function stack() {
  var keys = constant$1([]),
      order = none,
      offset = none$1,
      value = stackValue;

  function stack(data) {
    var sz = Array.from(keys.apply(this, arguments), stackSeries),
        i, n = sz.length, j = -1,
        oz;

    for (const d of data) {
      for (i = 0, ++j; i < n; ++i) {
        (sz[i][j] = [0, +value(d, sz[i].key, j, data)]).data = d;
      }
    }

    for (i = 0, oz = array(order(sz)); i < n; ++i) {
      sz[oz[i]].index = i;
    }

    offset(sz, oz);
    return sz;
  }

  stack.keys = function(_) {
    return arguments.length ? (keys = typeof _ === "function" ? _ : constant$1(Array.from(_)), stack) : keys;
  };

  stack.value = function(_) {
    return arguments.length ? (value = typeof _ === "function" ? _ : constant$1(+_), stack) : value;
  };

  stack.order = function(_) {
    return arguments.length ? (order = _ == null ? none : typeof _ === "function" ? _ : constant$1(Array.from(_)), stack) : order;
  };

  stack.offset = function(_) {
    return arguments.length ? (offset = _ == null ? none$1 : _, stack) : offset;
  };

  return stack;
}

function expand(series, order) {
  if (!((n = series.length) > 0)) return;