Long-Legged Doji

Install and import#

npm install fintech-algorithms

import { longLeggedDoji } from "fintech-algorithms/price-action-and-candlesticks/single-candle-patterns/long-legged-doji";

Signature#

longLeggedDoji(input)

Marks each bar whose body is a small fraction of its high-low span while both shadows are long, and reports how much slack the tightest of those three tests had.

Parameters#

Returns#

TopicResult

series.label is "neutral" on a matching bar and "none" otherwise. series.score is the minimum of the three margins (body_ratio minus body share, upper-shadow share minus shadow_ratio, lower-shadow share minus shadow_ratio), so it is at or above zero exactly when the bar matches. latest carries the last value of each. There is no warm-up: both series are populated from the first bar, so ready_at is 0.

Warm-up#

The first 0 bars positions are null. Every test is per-bar geometry with no smoothing state, so label and score are emitted for index 0 and ready_at is 0. The one gap is a flat bar where high equals low: score is null there and label is "none", which is a real verdict rather than a warm-up placeholder.

Errors#

• When a bar has a non-finite price or volume, a negative volume, a high below its own open/low/close, a low above them, or a timestamp that does not advance — throws Error
• When body_ratio or shadow_ratio is not a finite number, or falls outside 0..1 — throws Error
• When input is not an object, input.parameters is not an object, or bars is not an array holding at least one bar — throws Error

Complexity: time O(n), space O(n).

Worked example#

executed Captured by running this function on the input its own test provides. Real output of real code — but not asserted against a published figure.

Input#

{
  "bars": [
    {
      "timestamp": "2024-01-02",
      "basis": "synthetic-unadjusted",
      "open": 100,
      "high": 101.45,
      "low": 98.695,
      "close": 100,
      "volume": 750000,
      "benchmark": 200
    },
    {
      "timestamp": "2024-01-03",
      "basis": "synthetic-unadjusted",
      "open": 101.49111452,
      "high": 103.38381693,
      "low": 100.05480022,
      "close": 101.78791214,
      "volume": 795117,
      "benchmark": 200.56326135
    },
    {
      "timestamp": "2024-01-04",
      "basis": "synthetic-unadjusted",
      "open": 102.45519048,
      "high": 104.6701838,
      "low": 100.91147007,
      "close": 102.9549389,
      "volume": 840234,
      "benchmark": 201.11020913
    }
  ],
  "parameters": {}
}

Call#

longLeggedDoji(input)

Returns#

object with 9 fields: topic_id, title, state, ready, ready_at, series, latest, parameters, …

{
  "topic_id": "D06-F02-A10",
  "title": "Long-Legged Doji",
  "state": "calculated",
  "ready": true,
  "ready_at": 0,
  "series": {
    "label": ["neutral", "none", "none", "none", "none", "neutral"],
    "score": [
      0.05,
      -0.03915474022958794,
      -0.08295729760191171,
      -0.08829149989844472,
      -0.0589777590581788,
      0.0044297342216514934
    ]
  },
  "latest": {
    "label": "none",
    "score": -0.06921211954649767
  },
  "parameters": {},
  "diagnostics": {
    "causal": true,
    "input_count": 96
  }
}

Diagrams#

Calculation flow#

flowchart LR
    A["one closed OHLC candle, tick size, prior-only reference sc"] --> B["Validate order, basis, and finite values"]
    B --> C["Apply the selected Long-Legged Doji convention"]
    C --> D["Emit value, readiness, and diagnostics"]
    D --> E["Interpret descriptively; test outcomes separately"]
    B -->|invalid or insufficient| X["Withhold output with a reason"]

stateDiagram-v2
    [*] --> Waiting
    Waiting --> Ready: enough valid causal observations
    Waiting --> Rejected: malformed or unsupported input
    Ready --> Calculated: selected formula applied
    Calculated --> Interpreted: diagnostic and limitation retained
    Interpreted --> Ready: next observation arrives
    Rejected --> Waiting: corrected input and deterministic reset

How it works#

This page states the contract — how to call it correctly. The article explains the concept: why it works, and where it breaks.

Read the article →

References#

• TA-Lib pattern-recognition catalog — see linked primary or authoritative record
• CME Group candlestick chart lesson — see linked primary or authoritative record
• Japanese Candlestick Charting Techniques — see linked primary or authoritative record
• Evidence decision
• Level 1 evidence map

The rest of the Single-Candle Patterns family#

• DojiEvaluates one candle against the repository's explicit doji geometry and scale convention.
• Dragonfly DojiEvaluates one candle against the repository's explicit dragonfly-doji geometry and scale convention.
• Gravestone DojiEvaluates one candle against the repository's explicit gravestone-doji geometry and scale convention.
• MarubozuEvaluates one candle against the repository's explicit marubozu geometry and scale convention.
• Spinning TopEvaluates one candle against the repository's explicit spinning-top geometry and scale convention.
• HammerEvaluates one candle against explicit hammer geometry, scale, and downtrend context conventions.
• Hanging ManEvaluates one candle against explicit hanging-man geometry, scale, and uptrend context conventions.
• Inverted HammerEvaluates one candle against explicit inverted-hammer geometry, scale, and downtrend context conventions.
• Shooting StarEvaluates one candle against explicit shooting-star geometry, scale, and uptrend context conventions.
• Four-Price DojiMarks each bar whose entire range and whose open-to-close distance both sit within a tick tolerance, the degenerate candle wher…
• High-Wave CandleMarks each bar with a small body relative to its high-low span whose two shadows are both a multiple of that body, the long-tai…
• Belt HoldMarks each bar that opens at one extreme of its own range within a tick and closes at least 60 percent of the span away, and re…