TD Combo

DeMark's stricter, faster countdown variant. Unlike vanilla TD Sequential (which only requires close <= low[i - 2] for a buy countdown), Combo adds two strictness conditions that prevent the countdown from advancing on weak bars: monotone non-rising lows and strictly-lower closes (mirrored for sells). The result is a faster, higher-conviction exhaustion signal.

Quick reference

Item	Value
Family	DeMark
Input type	Candle (uses high, low, close)
Output type	f64 — signed combo count
Output range	[-target, +target] (classic ±13)
Default parameters	(4, 9, 2, 13) — same as TdSequential
Warmup period	max(setup_lookback, countdown_lookback) + 1
Interpretation	+13 = buy combo complete; −13 = sell combo complete

Formula

Setup phase is identical to TdSetup (arms the combo after 9 consecutive bars satisfying the directional setup rule).

Buy combo bars must satisfy all three conditions:

1. close[i] <= low[i - 2]          // classic countdown rule
2. low[i]   <= low[i - 1]           // monotone non-rising lows
3. close[i] <  close[i - 1]          // strictly lower close

Sell combo bars must satisfy the mirror:

1. close[i] >= high[i - 2]
2. high[i]  >= high[i - 1]
3. close[i] >  close[i - 1]

The combo count saturates at target (DeMark's classic value is 13). See crates/wickra-core/src/indicators/td_combo.rs.

Parameters

Name	Type	Default	Description
setup_lookback	usize	4	Setup-phase lookback.
setup_target	usize	9	Setup count needed to arm.
countdown_lookback	usize	2	Countdown lookback (first condition).
countdown_target	usize	13	Combo target count.

Inputs / Outputs

Indicator<Input = Candle, Output = f64> — signed combo count. Same shape as TdCountdown. Python: 1-D np.ndarray with NaN warmup. Node: same.

Warmup

warmup_period() == max(setup_lookback, countdown_lookback) + 1.

Edge cases

• Stricter than vanilla Countdown. Many bars that would count in vanilla TD Countdown are filtered out by the additional monotone-low and strictly-lower-close conditions. Combo completes less often but with higher conviction.
• Opposite-direction setup invalidates. Same behaviour as TdCountdown.
• Reset. Clears all internal state.

Examples

Rust

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

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let prices: Vec<f64> = (0..40).map(|i| 100.0 - f64::from(i) * 0.6).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 = TdCombo::classic();
    let max = td.batch(&candles).iter().flatten().fold(0.0f64, |a, &b| a.max(b));
    println!("max buy combo: {max}");
    Ok(())
}

Python

import numpy as np
import wickra as ta

close = 100 - np.arange(40, dtype=float) * 0.6  # strict downtrend
td = ta.TdCombo()
print('max:', np.nanmax(td.batch(close + 0.3, close - 0.3, close)))

Node

const wickra = require('wickra');
const td = new wickra.TdCombo();
const close = Array.from({ length: 40 }, (_, i) => 100 - i * 0.6);
console.log('max:',
  Math.max(...td.batch(close.map(c => c + 0.3), close.map(c => c - 0.3), close)
              .filter(x => x != null)));

Streaming

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

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

Interpretation

• Higher conviction than vanilla. Combo completion requires monotone-non-rising lows and strictly-lower closes — capturing capitulation more strictly than vanilla Countdown's weaker close <= low[i - 2] rule.
• Faster in strong trends. Counter-intuitively, on a clean capitulation Combo can complete before vanilla Countdown, because the stricter conditions tend to be satisfied early in a clean panic-style drop and miss later "muddy" bars.
• Lower hit rate. Combos complete less often; many setups that would mature into Countdown 13 don't satisfy the Combo conditions.

Common pitfalls

• Using Combo as a drop-in for Sequential. Different conditions → different signal timing. Compare on historical data for the instrument before deploying.
• Resetting on session boundaries. Same as all DeMark indicators — do not reset on session boundaries.
• Ignoring Setup completion. Combo is armed by a completed setup; the same arming/invalidation rules apply as in TdCountdown.

References

• Tom DeMark, The New Science of Technical Analysis (1994) — TD Combo as the "aggressive countdown" variant.
• DeMark Indicators (with Jason Perl, 2008) — refined Combo rules and parameter guidance.

See also

• TdSequential — vanilla Setup + Countdown.
• TdCountdown — standalone vanilla countdown.
• TdSetup — setup phase.
• Indicators-Overview — full taxonomy.