stack.order()

stack.order([order])

If order is specified, sets the order accessor to the specified function or array and returns this stack generator. If order is not specified, returns the current order acccesor, which defaults to stackOrderNone; this uses the order given by the key accessor. See stack orders for the built-in orders.

If order is a function, it is passed the generated series array and must return an array of numeric indexes representing the stack order. For example, the default order is defined as:

function orderNone(series) {
  var n = series.length, o = new Array(n);
  while (--n >= 0) o[n] = n;
  return o;
}

The stack order is computed prior to the offset; thus, the lower value for all points is zero at the time the order is computed. The index attribute for each series is also not set until after the order is computed.