PriceChannel — Price Channel

The n-bar high, the n-bar low and their midline, delivered as one indicator — the Donchian channel when you want all three lines from a single declaration rather than three.

Signature

PriceChannel(period, on=<source>)

Argument	Type	Required	Notes
period	int Param or literal	Yes	Channel lookback. Default 20, bounds 1–400.
on=	symbol	No	Source symbol. Defaults to the trade symbol. Reads high and low.

Formula

$$ \text{upper} = \max(H, n), \quad \text{lower} = \min(L, n), \quad \text{mid} = \frac{\text{upper} + \text{lower}}{2} $$

Warmup

period bars; during the lead-in the channel covers the bars seen so far.

Reading the value

pc.upper
pc.mid
pc.lower

Multi-value: cannot be chained onto or crossed. Use DonchianHighTrue / DonchianLowTrue when you need value_at(1) for breakout logic or want to smooth a single line.

Example

class MidlineRevert(Strategy):
    """Buy the lower channel, exit at the midline."""
    trade = Symbol()
    sizing = FixedCapital()

    def execute(self):
        pc = PriceChannel(20, on=self.trade)
        if self.trade.close <= pc.lower and self.trade.is_flat:
            self.buy(self.trade, reason="At the channel low")
        if self.trade.close >= pc.mid and self.trade.is_long:
            self.sell(self.trade, self.trade.position, reason="Midline reached")

Notes

• Same computation as the true Donchian pair; shipped as one indicator for chart convenience.
• Proven by an assert-via-trade run on SPY daily (all three outputs matched a strategy-side rolling max/min to 1e-3 on every bar; zero alarm trades).
• The current bar is inside the channel, so close >= pc.upper is a touch, never a breakout — breakouts compare against the previous bar’s channel.