# Donchian Breakout

`D08-F07-A04` · Geometric Chart Patterns → Market Structure, Breakouts, and Regimes · archetype `record-transform` · difficulty 2/5 · verification **verified**

Full page: https://docs.thefintechbuilder.com/geometric-chart-patterns/market-structure-breakouts-and-regimes/donchian-breakout/
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 { donchianBreakout } from "fintech-algorithms/geometric-chart-patterns/market-structure-breakouts-and-regimes/donchian-breakout";
```

## Signature

```ts
donchianBreakout(input)
```

The Donchian channel over the preceding `period` bars plus the two breakout booleans it implies. This shares a byte-identical implementation with the single-asset new-high/new-low signal.

## Parameters

| Name | Type | Required | Notes |
| --- | --- | --- | --- |
| `input` | `TopicInput` | yes | `bars` is the required OHLCV history, strictly ordered by `timestamp` and on a single adjustment basis. `parameters.period` (default `20`, integer of at least 2) sets the channel lookback. |

## Returns

`TopicResult`

`series` and `latest` carry `upper`, `lower`, `new_high` and `new_low`. The warm-up is `period` bars because the channel excludes the current bar, so with the default `ready_at` is 20.

## Warm-up

The first `period bars (20 by default)` positions are `null`. The channel spans indices i-period through i-1, so index `period` is the first bar that has one.

## Errors

- When `period` is supplied as a non-integer or as a value below 2 — throws Error
- When `bars` is empty or is not an array — throws Error

## Complexity

Time `O(n × period)`, 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
donchianBreakout(input)
```

### Returns

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

```json
{
  "topic_id": "D08-F07-A04",
  "title": "Donchian Breakout",
  "state": "calculated",
  "ready": true,
  "ready_at": 20,
  "series": {
    "upper": [null, null, null, null, null, null],
    "lower": [null, null, null, null, null, null],
    "new_high": [null, null, null, null, null, null],
    "new_low": [null, null, null, null, null, null]
  },
  "latest": {
    "upper": 109.83623682,
    "lower": 99.69159419,
    "new_high": false,
    "new_low": false
  },
  "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/geometric-chart-patterns/market-structure-breakouts-and-regimes/donchian-breakout/
- Implementation source: https://github.com/IslamBaraka90/Fintech-Algorithms-Library/blob/main/src/geometric-chart-patterns/market-structure-breakouts-and-regimes/donchian-breakout/impl.ts
- Package on npm: https://www.npmjs.com/package/fintech-algorithms
- Domain index for agents: https://docs.thefintechbuilder.com/geometric-chart-patterns/llms.txt