# Belt Hold

`D06-F02-A13` · Price Action and Candlesticks → Single-Candle Patterns · archetype `record-transform` · difficulty 2/5 · verification **verified**

Full page: https://docs.thefintechbuilder.com/price-action-and-candlesticks/single-candle-patterns/belt-hold/
Agent skill: `npx skills add IslamBaraka90/Fintech-Algorithms-Library` — https://docs.thefintechbuilder.com/guides/agent-skill/

## Install and import

```bash
npm install fintech-algorithms
```

```ts
import { beltHold } from "fintech-algorithms/price-action-and-candlesticks/single-candle-patterns/belt-hold";
```

## Signature

```ts
beltHold(input)
```

Marks 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 reports that body share and which side it favoured.

## Parameters

| Name | Type | Required | Notes |
| --- | --- | --- | --- |
| `input` | `TopicInput` | yes | `bars` is a chronologically ordered array of OHLCV rows; each needs a non-empty `timestamp` strictly greater than the previous row's and finite `open`, `high`, `low`, `close` and `volume`. The single-candle family validates `body_ratio` (default 0.05), `shadow_ratio` (default 0.35), `shadow_body_multiple` (default 2) and `tick_tolerance` (default 0.01, at least 0) on every call, but this topic reads only `tick_tolerance`, how far the open may sit from the low (bullish) or the high (bearish). The 60 percent body share is fixed in the branch and is not configurable. |

## Returns

`TopicResult`

`series.label` is `"bullish"` when the bar closes up and opens within `tick_tolerance` of its low, `"bearish"` when it closes down and opens within `tick_tolerance` of its high, and `"none"` otherwise. `series.score` is the body as a share of the high-low span, between 0 and 1, reported on every bar with a positive range whether or not it matched. `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`. Per-bar geometry with no smoothing state, so `ready_at` is 0. On a flat bar where `high` equals `low` the positive-span guard leaves `score` null and `label` at `"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 `tick_tolerance` is not a finite number or is negative — 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

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

`input`:

```json
{
  "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

```ts
beltHold(input)
```

### Returns

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

```json
{
  "topic_id": "D06-F02-A13",
  "title": "Belt Hold",
  "state": "calculated",
  "ready": true,
  "ready_at": 0,
  "series": {
    "label": ["none", "none", "none", "none", "none", "none"],
    "score": [
      0,
      0.08915474022958794,
      0.13295729760191172,
      0.13829149989844472,
      0.1089777590581788,
      0.04557026577834851
    ]
  },
  "latest": {
    "label": "none",
    "score": 0.11921211954649767
  },
  "parameters": {},
  "diagnostics": {
    "causal": true,
    "input_count": 96
  }
}
```

## Verification and provenance

Tier: **verified** (via E).

The worked example below is the figure published in this algorithm's article, replayed and asserted by the test suite on every build. The arithmetic cannot drift without the build failing.

Both tiers guarantee the signature. Full explanation: https://docs.thefintechbuilder.com/guides/verification/

Generated from the docs.json payload shipped inside fintech-algorithms@0.13.0.
The signature and parameter list are checked against the compiled implementation at build time,
so a description that contradicts the code fails the build rather than reaching this file.

## Links

- Article (how it works, step by step): https://thefintechbuilder.com/price-action-and-candlesticks/single-candle-patterns/belt-hold/
- Implementation source: https://github.com/IslamBaraka90/Fintech-Algorithms-Library/blob/main/src/price-action-and-candlesticks/single-candle-patterns/belt-hold/impl.ts
- Package on npm: https://www.npmjs.com/package/fintech-algorithms
- Domain index for agents: https://docs.thefintechbuilder.com/price-action-and-candlesticks/llms.txt