LadderBottom

Five-bar bullish reversal. Three long black candles step the market down like rungs of a ladder, a fourth black candle finally shows an upper shadow (the first sign of buying), and a white candle then gaps up into its body to confirm the turn.

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 — LadderBottom::new()
Warmup period	5 (first four bars always 0.0)
Interpretation	Bottoming reversal after a stepped decline

Formula

bar1, bar2, bar3 black, with consecutively lower opens AND closes
bar4 black with an upper shadow      (high4 > open4)
bar5 white, opens above bar4's body   (open5 > open4) and closes up

Bullish-only (never −1.0). The fourth candle's upper shadow is the first hint of buying; the white fifth confirms. See crates/wickra-core/src/indicators/ladder_bottom.rs.

Parameters

None. Constructed with LadderBottom::new().

Signed ±1 encoding

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

Inputs / Outputs

use wickra::{Indicator, LadderBottom, Candle};
// LadderBottom: Input = Candle, Output = f64
const _: fn(&mut LadderBottom, Candle) -> Option<f64> = <LadderBottom 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() == 5. The first four bars return 0.0 (first_four_bars_return_zero, accessors_and_metadata).

Edge cases

• Fourth bar needs an upper shadow. Without it (the first buying hint) the result is 0.0 (fourth_bar_without_upper_shadow_yields_zero).
• First three must be descending blacks. Otherwise 0.0 (not_three_descending_blacks_yields_zero).
• Reset. reset() clears the four-bar cache (reset_clears_state).

Examples

Rust

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

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut t = LadderBottom::new();
    println!("{:?}", t.update(Candle::new(20.0, 20.1, 17.9, 18.0, 1.0, 0)?)); // black
    println!("{:?}", t.update(Candle::new(18.0, 18.1, 15.9, 16.0, 1.0, 1)?)); // lower black
    println!("{:?}", t.update(Candle::new(16.0, 16.1, 13.9, 14.0, 1.0, 2)?)); // lower black
    println!("{:?}", t.update(Candle::new(14.0, 15.0, 12.4, 12.5, 1.0, 3)?)); // black, upper shadow
    println!("{:?}", t.update(Candle::new(15.0, 17.1, 14.9, 17.0, 1.0, 4)?)); // white, gaps up
    Ok(())
}

Output:

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

Three descending blacks, a fourth black with an upper shadow (high 15 > open 14), then a white candle opening above it — a ladder bottom. This matches ladder_bottom_is_plus_one.

Python

import numpy as np
import wickra as ta

o = np.array([20.0, 18.0, 16.0, 14.0, 15.0])
h = np.array([20.1, 18.1, 16.1, 15.0, 17.1])
l = np.array([17.9, 15.9, 13.9, 12.4, 14.9])
c = np.array([18.0, 16.0, 14.0, 12.5, 17.0])

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

Node

const ta = require('wickra');
const t = new ta.LadderBottom();
t.update(20, 20.1, 17.9, 18);
t.update(18, 18.1, 15.9, 16);
t.update(16, 16.1, 13.9, 14);
t.update(14, 15, 12.4, 12.5);
console.log(t.update(15, 17.1, 14.9, 17)); // 1

Streaming

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

let mut t = LadderBottom::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) { /* stepped decline reversing */ }
}

Interpretation

1. Exhaustion of a staircase decline. Three orderly down-rungs, then the first buying wick, then a confirming white candle — a bullish bottom.
2. Rare. Five-bar reversals print infrequently; treat as a prompt to confirm.
3. Best at support. Strongest at the foot of an extended decline.

Common pitfalls

• Missing the fourth-bar shadow. The upper shadow on bar 4 is the defining early-buying signal; without it this is just a decline.
• No downtrend context. Only meaningful after a decline.

References

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

See also

• ConcealingBabySwallow — another rare multi-black bottoming pattern.
• RisingThreeMethods — five-bar bullish continuation.
• Indicators-Overview — the full taxonomy.