ConcealingBabySwallow

Rare four-bar bullish reversal. Two black marubozu lead a steep decline; the third is a black candle that gaps down on the open yet throws a long upper shadow back up into the second body; the fourth is a large black candle that completely engulfs the third, shadows included. Relentless selling that can no longer make ground signals capitulation.

Quick reference

Field	Value
Family	Candlestick Patterns
Input type	Candle
Output type	f64 — +1.0 bullish, 0.0 otherwise (never -1.0)
Output range	{0.0, +1.0}
Default parameters	none — ConcealingBabySwallow::new()
Warmup period	4 (first three bars always 0.0)
Interpretation	Capitulation bottom inside a steep downtrend

Formula

bar1, bar2 black marubozu (body ≈ range, shadows <= 5 % of range each)
bar3 black, opens below bar2's body:  open3 < close2          (downside open gap)
     with an upper shadow into it:    high3 > close2
bar4 black, engulfs bar3 incl. shadows:  open4 > high3  and  close4 < low3

black_marubozu(c) requires open > close, range > 0, and both shadows ≤ 5 % of range. The pattern is bullish-only (never −1.0): four black candles whose final, larger candle "swallows" the third yet fails to extend the decline is read as exhaustion. Thresholds are geometric, not TA-Lib rolling averages. See crates/wickra-core/src/indicators/concealing_baby_swallow.rs.

Parameters

None. Constructed with ConcealingBabySwallow::new().

Signed ±1 encoding

Single-direction shape: +1.0 bullish, 0.0 no pattern — one feature-matrix dimension.

Inputs / Outputs

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

• Always emits a value. Never None; warmup and no-match bars return 0.0.
• Node. update(open, high, low, close) → number; batch(open, high, low, close) → Array<number>.
• Python. update(candle) → float; batch(open, high, low, close) → 1-D numpy.ndarray (0.0 on warmup / no-match).

Warmup

warmup_period() == 4. The first three bars return 0.0 (warmup_returns_zero, accessors_and_metadata).

Edge cases

• Leading bars not marubozu. A white or shadowed first/second candle yields 0.0 (first_bar_not_marubozu_yields_zero, second_bar_not_marubozu_yields_zero); a flat first bar is rejected through the marubozu range check (first_bar_zero_range_yields_zero).
• Third bar shape. It must be black (third_bar_not_black_yields_zero), gap below the second body (third_bar_no_gap_yields_zero), and reach into it with an upper shadow (third_bar_no_upper_shadow_yields_zero).
• Fourth bar must engulf shadows. A non-black or non-engulfing fourth candle yields 0.0 (fourth_bar_not_black_yields_zero, fourth_bar_not_engulfing_yields_zero).
• Reset. reset() clears the three-bar cache (reset_clears_state).

Examples

Rust

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

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut t = ConcealingBabySwallow::new();
    println!("{:?}", t.update(Candle::new(20.0, 20.1, 14.9, 15.0, 1.0, 0)?)); // black marubozu
    println!("{:?}", t.update(Candle::new(16.0, 16.1, 11.9, 12.0, 1.0, 1)?)); // black marubozu
    println!("{:?}", t.update(Candle::new(11.0, 13.0, 9.9, 10.0, 1.0, 2)?));  // black, gap + upper shadow
    println!("{:?}", t.update(Candle::new(14.0, 14.1, 8.9, 9.0, 1.0, 3)?));   // black, engulfs bar3
    Ok(())
}

Output:

Some(0.0)
Some(0.0)
Some(0.0)
Some(1.0)

The fourth candle opens at 14.0 (above high3 = 13.0) and closes at 9.0 (below low3 = 9.9), engulfing the third including its shadows. This matches concealing_baby_swallow_is_plus_one.

Python

import numpy as np
import wickra as ta

o = np.array([20.0, 16.0, 11.0, 14.0])
h = np.array([20.1, 16.1, 13.0, 14.1])
l = np.array([14.9, 11.9, 9.9,  8.9])
c = np.array([15.0, 12.0, 10.0, 9.0])

print(ta.ConcealingBabySwallow().batch(o, h, l, c))  # [0. 0. 0. 1.]

Node

const ta = require('wickra');
const t = new ta.ConcealingBabySwallow();
t.update(20, 20.1, 14.9, 15);
t.update(16, 16.1, 11.9, 12);
t.update(11, 13, 9.9, 10);
console.log(t.update(14, 14.1, 8.9, 9)); // 1

Streaming

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

let mut t = ConcealingBabySwallow::new();
let candle_stream: Vec<wickra::Candle> = Vec::new(); // your live OHLCV candle feed
for bar in candle_stream {
    if t.update(bar) == Some(1.0) { /* rare capitulation bottom — confirm before acting */ }
}

Interpretation

1. Capitulation, not strength. All four candles are black — the bullish read comes from the failure to extend after a wide engulfing bar, classic seller exhaustion at the end of a steep decline.
2. Very rare. One of the least frequent classical patterns; expect almost no prints on most series. Treat any signal as a prompt to look for confirmation, not a standalone entry.
3. Confirm aggressively. Because it is bullish despite four down candles, require follow-through (a white candle, a momentum turn) before trusting it.

Common pitfalls

• Loosening the marubozu test. The first two candles must be near-shadowless; ordinary black candles do not qualify.
• Partial engulf. The fourth candle must engulf the third's shadows, not just its body.

References

• Steve Nison, Japanese Candlestick Charting Techniques (1991).

See also

• LadderBottom — another multi-black bullish bottoming pattern.
• ThreeStarsInSouth — three-bar bearish-looking bottoming setup.
• Indicators-Overview — the full taxonomy.