MarketFacilitationIndex — Market Facilitation Index

Bar range per unit of volume: how much price movement each contract bought. Bill Williams reads it in a 2×2 with volume’s own direction — MFI up on rising volume is a real move; MFI up on falling volume is a move nobody is defending.

Signature

MarketFacilitationIndex(period, scale, on=<source>)

Argument	Type	Required	Notes
period	int Param or literal	Yes	SMA smoothing. 1 returns the raw per-bar value. Bounds 1–200.
scale	int Param or literal	Yes	Volume divisor keeping the value readable. Default 1,000,000. Bounds 1–1e9.
on=	symbol	No	Source symbol. Defaults to the trade symbol. Reads high, low, volume.

Formula

$$ \text{MFI} = \frac{H - L}{V / \text{scale}} $$

Warmup

period bars; zero-volume bars contribute 0.

Reading the value

mfi.value
mfi.value > mfi.value_at(1)

Example

class FacilitationRead(Strategy):
    """Williams' green bar: facilitation and volume both rising."""
    trade = Symbol()
    sizing = FixedCapital()

    def execute(self):
        mfi = MarketFacilitationIndex(1, 1000000, on=self.trade)
        rv = RelativeVolume(20, on=self.trade)
        if mfi.value > mfi.value_at(1) and rv.value > 1 and self.trade.is_flat:
            self.buy(self.trade, reason="Movement and participation both up")
        if mfi.value < mfi.value_at(1) and self.trade.is_long:
            self.sell(self.trade, self.trade.position, reason="Facilitation falling")

Notes

• Bill Williams, Trading Chaos (1995). Not the same as MoneyFlowIndex despite sharing the MFI abbreviation.