# Range Efficiency Ratio

`D07-F06-A09` · Technical Indicators → Range and Volatility Indicators · archetype `series-transform` · difficulty 2/5 · verification **verified**

Full page: https://docs.thefintechbuilder.com/technical-indicators/range-and-volatility-indicators/range-efficiency-ratio/
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 { rangeEfficiencyRatio } from "fintech-algorithms/technical-indicators/range-and-volatility-indicators/range-efficiency-ratio";
```

## Signature

```ts
rangeEfficiencyRatio(input)
```

Range Efficiency Ratio: the absolute net close-to-close move across `period` bars divided by the sum of the high-low ranges over the same span.

## Parameters

| Name | Type | Required | Notes |
| --- | --- | --- | --- |
| `input` | `TopicInput` | yes | `bars` is the required OHLCV array -- each bar carries `timestamp`, `open`, `high`, `low`, `close`, `volume` and an optional `basis`, strictly ordered by timestamp. From `parameters` this topic reads only `period` (default 14, integer >= 2), which sets both the close lookback and the range-summing window. |

## Returns

`TopicResult`

`series` holds a single key, `value`, a 0-1 efficiency reading; `latest.value` is its last value. The warm-up is `period` leading nulls, so `ready_at` is 14 at the default period.

## Warm-up

The first ``period` bars (14 at the default period)` positions are `null`. The numerator compares the close against the close `period` bars earlier, so it needs one more bar than the range window does. `value` is also null on any bar where the summed range is zero.

## Errors

- When `parameters.period` is not an integer >= 2 — throws Error
- When a bar is missing open, high, low, close, or volume, or one of them is not a finite number — throws Error
- When bars are not strictly ordered by timestamp, or a bar's high is below its open, low, or close — 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
rangeEfficiencyRatio(input)
```

### Returns

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

```json
{
  "topic_id": "D07-F06-A09",
  "title": "Range Efficiency Ratio",
  "state": "calculated",
  "ready": true,
  "ready_at": 14,
  "series": {
    "value": [null, null, null, null, null, null]
  },
  "latest": {
    "value": 0.07606679254426744
  },
  "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/technical-indicators/range-and-volatility-indicators/range-efficiency-ratio/
- Implementation source: https://github.com/IslamBaraka90/Fintech-Algorithms-Library/blob/main/src/technical-indicators/range-and-volatility-indicators/range-efficiency-ratio/impl.ts
- Package on npm: https://www.npmjs.com/package/fintech-algorithms
- Domain index for agents: https://docs.thefintechbuilder.com/technical-indicators/llms.txt