TdPropulsion

Tom DeMark's TD Propulsion — a two-bar continuation thrust: open on the trend side of the prior close, then close beyond the prior bar's extreme.

Quick reference

Field	Value
Family	DeMark
Input type	Candle (open / high / low / close)
Output type	f64 (signed signal)
Output range	{−1, 0, +1}
Default parameters	None (parameter-free)
Warmup period	2
Interpretation	+1 upside thrust; −1 downside thrust.

Formula

Up   (+1): open >= close[-1]  AND  close > high[-1]
Down (−1): open <= close[-1]  AND  close < low[-1]
otherwise 0

A bar that opens at or above the prior close and then closes above the prior high "propels" an advance forward — a continuation thrust. The down case mirrors it. Source: crates/wickra-core/src/indicators/td_propulsion.rs.

Parameters

Name	Type	Default	Valid range	Source	Description
—	—	—	—	None.	TD Propulsion is parameter-free; TdPropulsion::new() is infallible.

Signed ±1 encoding

+1.0 upside thrust, −1.0 downside thrust, 0.0 no thrust (warmup emits None).

Inputs / Outputs

From crates/wickra-core/src/indicators/td_propulsion.rs:

use wickra::{Candle, Indicator, TdPropulsion};
// TdPropulsion: Input = Candle, Output = f64
const _: fn(&mut TdPropulsion, Candle) -> Option<f64> = <TdPropulsion as Indicator>::update;

A Candle in, an Option<f64> out. Python update(candle) / batch(open, high, low, close); Node update(open, high, low, close) / batch(...).

Warmup

warmup_period() == 2. The first candle seeds the prior bar (first_bar_seeds_without_signal pins this).

Edge cases

• Up thrust. Open ≥ prior close and close > prior high → +1 (propulsion_up pins this).
• Down thrust. The mirror → −1 (propulsion_down pins this).
• No thrust → 0. (no_thrust_is_zero pins this).
• Finiteness. Candle::new rejects non-finite fields, so no in-method guard is needed.
• Reset. td.reset() clears the prior bar and the last value (reset_clears_state).

Examples

Rust

use wickra::{Candle, Indicator, TdPropulsion};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut td = TdPropulsion::new();
    td.update(Candle::new(9.5, 11.0, 9.0, 10.0, 0.0, 0)?);
    let sig = td.update(Candle::new(10.5, 12.0, 10.0, 11.5, 0.0, 0)?);
    println!("{:?}", sig); // Some(1.0)
    Ok(())
}

Output:

Some(1.0)

Python

import numpy as np
import wickra as ta

td = ta.TdPropulsion()
o = np.array([9.5, 10.5]); h = np.array([11, 12]); l = np.array([9, 10]); c = np.array([10, 11.5])
print(td.batch(o, h, l, c))  # [nan, 1.0]

Node

const ta = require('wickra');
const td = new ta.TdPropulsion();
td.update(9.5, 11, 9, 10);
console.log(td.update(10.5, 12, 10, 11.5)); // 1

Streaming

use wickra::{Candle, Indicator, TdPropulsion};

let mut td = TdPropulsion::new();
let feed: Vec<Candle> = Vec::new(); // your live stream
for candle in feed {
    if let Some(s) = td.update(candle) { let _ = s; }
}

Streaming update and batch are equivalent tick-for-tick (batch_equals_streaming pins this).

Interpretation

1. Continuation confirmation. Use it to add to or hold a trend position when a thrust confirms momentum.
2. Breakout quality. A propulsion bar through resistance is a stronger break than a drift through it.
3. Combine with Setup. DeMark traders use propulsion to validate moves inside a Setup/Countdown.

Common pitfalls

• Continuation, not reversal. Propulsion confirms the existing direction; do not read it as a turn.
• Open dependence. The open vs. prior close gate matters — gappy instruments behave differently.
• One bar. Pair with structure for context.

References

Perl, J. (2008), DeMark Indicators, Bloomberg Press.

See also

• Indicator-TdSetup — the DeMark setup count.
• Indicator-TdTrap — inside-bar breakout.
• Indicator-Marubozu — full-body thrust bar.
• Indicators-Overview — the full taxonomy.