WilliamsClose — Williams Close

A Williams %R variant computed on closes: how far the current close sits below the highest close of the window, on a −100–0 scale.

WilliamsClose is the identifier a strategy writes; Williams Close is the label the chart’s indicator picker shows. Single value — .value is the only accessor.

Signature

WilliamsClose(period, on=<source>)

Argument	Type	Required	Notes
period	int Param or literal	Yes	Lookback window. Default 14, bounds 5–100.
on=	symbol, OHLCV field, or indicator	No	Source. Defaults to the trade symbol’s close.

Formula

Over the last N values of the source:

$$ \text{WilliamsClose} = \frac{\max - \text{close}_t}{\max(\max - \min,\ 0.0001)} \times -100 $$

0 means the close is the highest of the window (overbought), -100 means it is the lowest (oversold), -50 is mid-range. The denominator is floored at a small epsilon so a flat window cannot divide by zero.

Warmup

period bars. Before the window fills, the indicator returns -50 — the neutral midpoint of its own scale, not 0. A strategy never observes it (execute() waits until every indicator is ready); it is what the chart plots on the leading bars.

Reading the value

wr.value                  # -100..0
wr.value_at(1)
wr < -80                  # oversold
wr > -20                  # overbought
wr.crossed_above(-80)     # the bar it leaves oversold

Example

class WilliamsReversion(Strategy):
    """Buy deep oversold readings, exit as price returns to the top of the range."""
    period = Param(14, min=5, max=100)
    trade = Symbol()
    sizing = FixedCapital()

    def execute(self):
        wr = WilliamsClose(self.period, on=self.trade)
        self.stop_loss(3.0)

        if wr.crossed_above(-80) and self.trade.is_flat:
            self.buy(self.trade, reason=f"Leaving oversold ({wr.value:.0f})")

        if wr.value > -20 and self.trade.is_long:
            self.sell(self.trade, self.trade.position, reason="Back at the range high")

Notes

• Every threshold is negative. wr.value > 80 can never be true — the scale tops out at 0. Overbought is > -20; oversold is < -80. This is the single most common mistake with this indicator.
• A perfectly flat window reads 0 — the overbought end — because the numerator collapses to zero while the epsilon-floored denominator keeps the division finite. Treat a zero-range window as no signal, not as a top.
• This is StochasticClose inverted and shifted: WilliamsClose = StochasticClose − 100. Pick whichever scale you find easier to read; they carry the same information.
• Close-only, so wicks never move it. The classic Williams %R uses the window’s highest high and lowest low.