# Hilbert Transform Dominant Cycle Period

`D09-F06-A01` · Statistical Time Series → Hilbert and Ehlers Cycle Analytics · archetype `record-transform` · difficulty 2/5 · verification **verified**

Full page: https://docs.thefintechbuilder.com/statistical-time-series/hilbert-and-ehlers-cycle-analytics/hilbert-transform-dominant-cycle-period/
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 { hilbertTransformDominantCyclePeriod } from "fintech-algorithms/statistical-time-series/hilbert-and-ehlers-cycle-analytics/hilbert-transform-dominant-cycle-period";
```

## Signature

```ts
hilbertTransformDominantCyclePeriod(input)
```

Estimates the dominant cycle length in bars from the bar-to-bar change in the Hilbert phase angle, clamping each raw estimate into the 6-to-50 bar range and smoothing it with a 0.2 / 0.8 exponential update. Any contract failure is rethrown as an `Error` whose message begins `topic calculation failed: `.

## Parameters

| Name | Type | Required | Notes |
| --- | --- | --- | --- |
| `input` | `TopicInput` | yes | `bars` is a non-empty array of rows with `timestamp`, `open`, `high`, `low`, `close` and `volume`, strictly ordered by timestamp. The cycles family reads one key from `parameters`, `period`, defaulting to 20 and required to be an integer of at least 4; it is validated for this topic but its arithmetic never uses it. |

## Returns

`TopicResult`

`series.value` and `latest.value` carry the smoothed dominant-cycle period measured in bars, always between 6 and 50. `parameters` echoes the supplied parameters and `diagnostics` reports `causal` and `input_count`. Warm-up is seven leading nulls, so `ready_at` is 7.

## Warm-up

The first `7` positions are `null`. The 4-bar EMA of `close` first resolves at index 3, the four-tap quadrature filter needs three further bars so phase begins at index 6, and the period step differences two consecutive phases, which puts the first estimate and `ready_at` at index 7.

## Errors

- When `parameters.period` is present but is not an integer of at least 4 — throws Error
- When `bars` is empty, a `timestamp` is missing or not strictly increasing, an OHLCV field is not finite, `volume` is negative, or `high` and `low` do not bracket `open` and `close` — 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
hilbertTransformDominantCyclePeriod(input)
```

### Returns

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

```json
{
  "topic_id": "D09-F06-A01",
  "title": "Hilbert Transform Dominant Cycle Period",
  "state": "calculated",
  "ready": true,
  "ready_at": 7,
  "series": {
    "value": [null, null, null, null, null, null]
  },
  "latest": {
    "value": 24.86605208112273
  },
  "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/statistical-time-series/hilbert-and-ehlers-cycle-analytics/hilbert-transform-dominant-cycle-period/
- Implementation source: https://github.com/IslamBaraka90/Fintech-Algorithms-Library/blob/main/src/statistical-time-series/hilbert-and-ehlers-cycle-analytics/hilbert-transform-dominant-cycle-period/impl.ts
- Package on npm: https://www.npmjs.com/package/fintech-algorithms
- Domain index for agents: https://docs.thefintechbuilder.com/statistical-time-series/llms.txt