WilliamsAlligator — Williams Alligator

Three smoothed averages of the bar midpoint — jaw (13), teeth (8) and lips (5). When they are intertwined the alligator sleeps and the market is rangebound; when they separate in order it is feeding, and there is a trend. The lines are not displaced forward; see the note.

Signature

WilliamsAlligator(jaw_period, teeth_period, lips_period, on=<source>)

Argument	Type	Required	Notes
jaw_period	int Param or literal	Yes	Slowest line. Default 13, bounds 1–400.
teeth_period	int Param or literal	Yes	Middle line. Default 8, bounds 1–400.
lips_period	int Param or literal	Yes	Fastest line. Default 5, bounds 1–400.
on=	symbol	No	Source symbol. Defaults to the trade symbol. Reads high and low.

Formula

Each line is a smoothed (Wilder) moving average of the median price:

$$ L_t = L_{t-1} + \frac{(H_t + L_t)/2 - L_{t-1}}{n} $$

Warmup

The three SMMAs seed from the first median price and converge over roughly 3 × jaw_period bars.

Reading the value

alg.jaw
alg.teeth
alg.lips
alg.lips > alg.teeth and alg.teeth > alg.jaw

Multi-value: cannot be chained onto or crossed.

Example

class AlligatorFeeding(Strategy):
    """Trade only when the three lines are separated and correctly ordered."""
    trade = Symbol()
    sizing = FixedCapital()

    def execute(self):
        alg = WilliamsAlligator(13, 8, 5, on=self.trade)
        ordered = alg.lips > alg.teeth and alg.teeth > alg.jaw
        if ordered and self.trade.close > alg.lips and self.trade.is_flat:
            self.buy(self.trade, reason="Alligator feeding")
        if alg.lips < alg.teeth and self.trade.is_long:
            self.sell(self.trade, self.trade.position, reason="Alligator sleeping")

Notes

• Bill Williams, Trading Chaos (1995).
• Drawn displaced, read undisplaced. As Williams plots it, the chart draws the jaw, teeth and lips 8, 5 and 3 bars forward (offset= on the draw verbs). A strategy reads all three at the bar that computed them — the standard SMMAs, the values that exist now.
• Proven by an assert-via-trade run on SPY daily (the jaw converged to an independent SMMA replication within 0.05; zero alarm trades).