# Vortex Indicator (+VI/−VI)

`D07-F02-A10` · Technical Indicators → Trend Systems · archetype `series-transform` · difficulty 2/5 · verification **verified**

Full page: https://docs.thefintechbuilder.com/technical-indicators/trend-systems/vortex-indicator-vi-vi/
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 { vortexIndicatorViVi } from "fintech-algorithms/technical-indicators/trend-systems/vortex-indicator-vi-vi";
```

## Signature

```ts
vortexIndicatorViVi(input)
```

Sums the upward and downward vortex movements over a rolling window and divides each by the summed true range, giving the paired `plus_vi` and `minus_vi` lines.

## Parameters

| Name | Type | Required | Notes |
| --- | --- | --- | --- |
| `input` | `TopicInput` | yes | `bars` is the OHLCV series, validated for finite prices, strictly increasing `timestamp`, a single adjustment `basis`, non-negative `volume`, and a high and low that bracket the other prices. From `parameters` this topic reads only `period` (integer, minimum 2, default 14), the length of both the movement sums and the true-range sum. |

## Returns

`TopicResult`

`series` and `latest` carry `plus_vi` and `minus_vi`, and nothing else. Both share one warm-up, and either is null on any bar whose true-range sum is zero.

## Warm-up

The first `period bars (14 by default)` positions are `null`. The vortex movements are undefined on the first bar, so the first complete window ends one bar later than a plain rolling sum would: with the default period, indices 0 to 13 are null and `ready_at` is 14.

## Errors

- When `parameters.period` is present but is not an integer of at least 2 — throws Error
- When `bars` is empty, or a bar has a non-finite price, a negative volume, a timestamp not greater than the previous one, or a high 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
vortexIndicatorViVi(input)
```

### Returns

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

```json
{
  "topic_id": "D07-F02-A10",
  "title": "Vortex Indicator (+VI/−VI)",
  "state": "calculated",
  "ready": true,
  "ready_at": 14,
  "series": {
    "plus_vi": [null, null, null, null, null, null],
    "minus_vi": [null, null, null, null, null, null]
  },
  "latest": {
    "plus_vi": 0.91078566552092,
    "minus_vi": 1.0406526774370142
  },
  "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/trend-systems/vortex-indicator-vi-vi/
- Implementation source: https://github.com/IslamBaraka90/Fintech-Algorithms-Library/blob/main/src/technical-indicators/trend-systems/vortex-indicator-vi-vi/impl.ts
- Package on npm: https://www.npmjs.com/package/fintech-algorithms
- Domain index for agents: https://docs.thefintechbuilder.com/technical-indicators/llms.txt