Engulfing

Two-bar reversal pattern. The current candle's body fully engulfs the prior candle's body and points in the opposite direction. One of the strongest single-name candlestick reversal patterns — visually striking and statistically reasonably reliable.

Quick reference

Item	Value
Family	Candlestick Patterns
Input type	Candle
Output type	f64 — +1.0 bullish, -1.0 bearish, 0.0 otherwise
Output range	{-1.0, 0.0, +1.0}
Default parameters	none — Engulfing::new()
Warmup period	2
Interpretation	Two-bar reversal; bullish engulfing at lows, bearish at highs

Formula

prev_body = |prev.close - prev.open|
curr_body = |curr.close - curr.open|

bullish (+1.0): prev red AND curr green
              AND curr.open <= prev.close
              AND curr.close >= prev.open
              AND curr_body > prev_body

bearish (-1.0): prev green AND curr red
              AND curr.open >= prev.close
              AND curr.close <= prev.open
              AND curr_body > prev_body

Output is 0.0 for the first bar (no previous). See crates/wickra-core/src/indicators/engulfing.rs.

Parameters

None.

Signed ±1 encoding

This pattern already emits the uniform candlestick sign convention shared across the family — +1.0 bullish, −1.0 bearish, 0.0 no pattern — so it drops straight into a machine-learning feature matrix where the bullish and bearish variants of the pattern occupy a single dimension.

Inputs / Outputs

Indicator<Input = Candle, Output = f64>. Python / Node: same shape as other multi-bar candlestick patterns (first bar NaN / null).

Warmup

warmup_period() == 2. First bar always returns 0.0.

Edge cases

• Equal bodies. Strict > requires the engulfing body to be larger; equal-size bodies don't qualify.
• Doji as prior bar. prev_body == 0 means curr_body > 0 trivially holds — but the colour test (prev red / prev green) fails when the prior bar is a doji, so engulfing doesn't fire on doji-followed-by-large-body. Use MorningEveningStar for that pattern.
• Reset. Clears the previous-bar cache.

Examples

Rust

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

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let prev = Candle::new(100.0, 101.0, 99.0, 99.5, 1.0, 0)?;  // red
    let curr = Candle::new(99.4, 102.0, 99.0, 101.5, 1.0, 1)?;   // green, engulfs
    let mut e = Engulfing::new();
    e.update(prev);
    println!("{:?}", e.update(curr));  // +1.0 (bullish engulfing)
    Ok(())
}

Python

import numpy as np
import wickra as ta

o = np.array([100.0, 99.4])
h = np.array([101.0, 102.0])
l = np.array([99.0,  99.0])
c = np.array([99.5,  101.5])

e = ta.Engulfing()
print(e.batch(o, h, l, c))  # [0.0, 1.0]

Node

const wickra = require('wickra');
const e = new wickra.Engulfing();
console.log(e.batch([100, 99.4], [101, 102], [99, 99], [99.5, 101.5]));

Streaming

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

let mut e = Engulfing::new();
let candle_stream: Vec<wickra::Candle> = Vec::new(); // your live OHLCV candle feed
for bar in candle_stream {
    let v = e.update(bar);
    if v == Some(1.0) { /* bullish engulfing */ }
    if v == Some(-1.0) { /* bearish engulfing */ }
}

Interpretation

• Bullish engulfing at lows. Strong reversal candidate after a downtrend or near support. The full-body reversal signals significant sentiment shift.
• Bearish engulfing at highs. Mirror signal at the top of an uptrend or near resistance.
• Pair with confirmation. ThreeOutside is the confirmed three-bar variant — adds a third bar that closes beyond the engulfing close.

Common pitfalls

• Body-only check. Engulfing requires the body (open-to-close) to engulf, not the full bar range. Wicks are ignored.
• Without trend context. A "bullish engulfing" in a downtrending consolidation is often just a noise bounce. Pair with a trend / extreme filter.
• Equal-body bars. Strict > requirement — body sizes can be very close, but must not be equal.

References

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

See also

• Harami — opposite pattern (small inside large body).
• ThreeOutside — confirmed three-bar Engulfing variant.
• PiercingDarkCloud — softer two-bar reversal pattern.
• Indicators-Overview — full taxonomy.