TD Sequential

The full Tom DeMark Sequential indicator: a Setup count followed by a Countdown count. Setup runs the 9-bar momentum-exhaustion gate, Countdown then runs a separate 13-bar confirmation; together a completed Sequential is the canonical DeMark exhaustion signal. DeMark's bar-13 qualifier is enforced: the final countdown bar must also trade through the close of countdown bar 8, or it is deferred. Emits both phases in a single Output so the caller can read setup progress and countdown progress in one shot.

Quick reference

Item	Value
Family	DeMark
Input type	Candle (uses high, low, close)
Output type	TdSequentialOutput { setup, countdown, direction: f64 } (signed: positive = buy, negative = sell)
Output range	setup ∈ [-setup_target, setup_target], countdown ∈ [-countdown_target, countdown_target]
Default parameters	setup_lookback=4, setup_target=9, countdown_lookback=2, countdown_target=13
Warmup period	max(setup_lookback, countdown_lookback) + 1
Interpretation	Buy (setup=9, countdown=13) or sell (-9, -13) signals momentum exhaustion

Formula

Setup phase — same as TdSetup:

if close[t] < close[t - setup_lookback]:  buy_setup_streak += 1
if close[t] > close[t - setup_lookback]:  sell_setup_streak += 1
streak resets on the opposite direction or on equality

Once buy_setup_streak == setup_target (9), the Countdown phase arms. From the next bar:

if close[t] <= low[t - countdown_lookback]:   buy_countdown += 1
if close[t] >= high[t - countdown_lookback]:  sell_countdown += 1

Countdown bars do not need to be consecutive. The final bar is subject to DeMark's bar-13 qualifier: besides meeting the comparison above, it must trade through the close of countdown bar countdown_target − 5 (bar 8 of 13):

buy  bar 13 counts only if  low[t]  <= close[countdown bar 8]
sell bar 13 counts only if  high[t] >= close[countdown bar 8]
otherwise the bar is deferred (count stays at 12)

Countdown completes at countdown_target (13). When countdown_target <= 5 there is no bar countdown_target − 5, so no qualifier applies. See crates/wickra-core/src/indicators/td_sequential.rs.

Parameters

Name	Type	Default	Description
setup_lookback	usize	4	Setup-phase close-vs-close lookback.
setup_target	usize	9	Setup-phase target count (Setup 9).
countdown_lookback	usize	2	Countdown-phase close-vs-high/low lookback.
countdown_target	usize	13	Countdown-phase target count (Countdown 13).

TdSequential::classic() constructs (4, 9, 2, 13). new returns Error::PeriodZero for any zero argument.

Inputs / Outputs

Indicator<Input = Candle, Output = TdSequentialOutput>. TdSequentialOutput carries setup: f64, countdown: f64 and direction: f64. setup and countdown are signed (positive = buy-side counts, negative = sell-side); direction is +1.0 while a buy countdown is active, -1.0 for a sell countdown, 0.0 otherwise.

• Python. update returns a (setup, countdown, direction) 3-tuple per bar; batch returns an (n, 3) matrix.
• Node. update returns { setup, countdown, direction } | null per bar; batch returns a flat number[] of length n * 3 ([setup0, countdown0, direction0, setup1, ...]).

Warmup

warmup_period() == max(setup_lookback, countdown_lookback) + 1 — fundamentally the same close-buffer requirement as TD Setup, just with both lookbacks available.

Edge cases

• Setup completes before Countdown can arm. Buy Setup 9 arms Buy Countdown; if a sell-side momentum bar then prints, the Buy Setup counter doesn't reset, but Buy Countdown bars don't increment either.
• Countdown interrupted. Countdown counts can sit at a partial value (e.g. 7/13) across many bars while waiting for the next qualifying close.
• Deferred bar 13. A bar that meets the countdown comparison while the count is at 12 but does not trade through the close of countdown bar 8 (buy: low > close₈; sell: high < close₈) is deferred — the count stays at 12 until a later bar satisfies both conditions.
• Opposite-direction invalidation. A sell setup completion can invalidate an active buy countdown — output direction flips and the stored bar-8 qualifier close is cleared.
• Reset. reset() clears both setup and countdown streaks and the bar-8 qualifier close.

Examples

Rust

use wickra::{BatchExt, Candle, Indicator, TdSequential};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let prices: Vec<f64> = (0..60).map(|i| 100.0 - f64::from(i) * 0.4).collect();
    let candles: Vec<Candle> = prices.iter().enumerate()
        .map(|(i, &c)| Candle::new(c, c + 0.3, c - 0.3, c, 1.0, i as i64).unwrap())
        .collect();
    let mut td = TdSequential::classic();
    for c in &candles {
        if let Some(o) = td.update(*c) {
            if o.countdown == 13.0 { println!("buy countdown complete"); }
            if o.countdown == -13.0 { println!("sell countdown complete"); }
        }
    }
    Ok(())
}

Python

import numpy as np
import wickra as ta

close = 100 - np.arange(60, dtype=float) * 0.4
td = ta.TDSequential()
out = td.batch(close + 0.3, close - 0.3, close)
# out shape (60, 3): columns [setup, countdown, direction]
print('row 30:', out[30])

Node

const wickra = require('wickra');
const td = new wickra.TDSequential(4, 9, 2, 13);
const close = Array.from({ length: 60 }, (_, i) => 100 - i * 0.4);
const flat = td.batch(close.map(c => c + 0.3), close.map(c => c - 0.3), close);
console.log('row 30: setup =', flat[30 * 3], 'countdown =', flat[30 * 3 + 1]);

Streaming

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

let mut td = TdSequential::classic();
let candle_stream: Vec<wickra::Candle> = Vec::new(); // your live OHLCV candle feed
for bar in candle_stream {
    if let Some(o) = td.update(bar) {
        if o.countdown == 13.0 { /* high-conviction buy */ }
        if o.countdown == -13.0 { /* high-conviction sell */ }
    }
}

Interpretation

• Buy Setup 9 → Buy Countdown 13. Capitulation-grade oversold — high-conviction long mean-reversion signal.
• Sell Setup 9 → Sell Countdown 13. Mirror — distribution topping signal.
• Setup 9 without Countdown 13. Momentum extreme but not the full DeMark setup-and-cool-off pattern. Still tradable as a short-term reversal setup, just with lower historical hit rate.
• Risk management. Pair with TdLines for invalidation levels and TdRiskLevel for protective stops.

Common pitfalls

• Trading on Setup 9 alone. Setup 9 is the gate, Countdown 13 is the entry. Mixing them up halves the signal's edge.
• Resetting Countdown manually on session boundaries. Sequential is bar-stream agnostic; do not reset on session boundaries.
• Ignoring direction. The signed output makes direction explicit; ignoring it produces inverted signals.
• Expecting 13 on the first comparison-qualifying bar. Because of the bar-13 qualifier, a bar can satisfy close <= low[t-2] (or close >= high[t-2]) at count 12 and still not complete the countdown. Implementations that skip the qualifier will print 13 earlier than Wickra.

References

• Tom DeMark, The New Science of Technical Analysis (1994) — original full Sequential treatment.
• DeMark on Day Trading Options (1999) — recycle, deferred countdown, and other edge-case rules. Wickra implements the bar-13 deferral (qualifier against the close of countdown bar 8); recycle is not implemented.

See also

• TdSetup — Setup-only variant.
• TdCountdown — Countdown-only variant.
• TdCombo — faster, stricter countdown variant.
• TdLines — TDST support/resistance lines.
• TdRiskLevel — protective-stop levels.
• Indicators-Overview — full taxonomy.