---
title: relativeStrengthIndex() function
description: relativeStrengthIndex() measures the relative speed and change of values in input tables.
url: https://docs.influxdata.com/flux/v0/stdlib/universe/relativestrengthindex/
estimated_tokens: 961
product: Flux
version: v0
publisher: InfluxData
canonical: https://docs.influxdata.com/flux/v0/stdlib/universe/relativestrengthindex/
date: '2024-04-08T16:01:02-06:00'
lastmod: '2024-04-08T16:01:02-06:00'
---

* Flux 0.38.0+

InfluxDB support

`relativeStrengthIndex()` measures the relative speed and change of values in input tables.

### Relative strength index (RSI) rules

* The general equation for calculating a relative strength index (RSI) is`RSI = 100 - (100 / (1 + (AVG GAIN / AVG LOSS)))`.
* For the first value of the RSI, `AVG GAIN` and `AVG LOSS` are averages of the `n` period.
* For subsequent calculations:
  * `AVG GAIN` = `((PREVIOUS AVG GAIN) * (n - 1)) / n`
  * `AVG LOSS` = `((PREVIOUS AVG LOSS) * (n - 1)) / n`

* `relativeStrengthIndex()` ignores `null` values.

### Output tables

For each input table with `x` rows, `relativeStrengthIndex()` outputs a table
with `x - n` rows.

##### Function type signature

```js
(<-tables: stream[A], n: int, ?columns: [string]) => stream[B] where A: Record, B: Record
```

For more information, see [Function type signatures](/flux/v0/function-type-signatures/).

## Parameters

### n

(Required)
Number of values to use to calculate the RSI.

### columns

Columns to operate on. Default is `["_value"]`.

### tables

Input data. Default is piped-forward data (`<-`).

## Examples

### Calculate a three point relative strength index

```js
import "sampledata"

sampledata.int()
    |> relativeStrengthIndex(n: 3)
```

[](#view-example-input-and-output)

View example input and output

#### Input data

|       \_time       |\_value|\*tag|
|--------------------|-------|-----|
|2021-01-01T00:00:00Z|  \-2  | t1  |
|2021-01-01T00:00:10Z|  10   | t1  |
|2021-01-01T00:00:20Z|   7   | t1  |
|2021-01-01T00:00:30Z|  17   | t1  |
|2021-01-01T00:00:40Z|  15   | t1  |
|2021-01-01T00:00:50Z|   4   | t1  |

|       \_time       |\_value|\*tag|
|--------------------|-------|-----|
|2021-01-01T00:00:00Z|  19   | t2  |
|2021-01-01T00:00:10Z|   4   | t2  |
|2021-01-01T00:00:20Z|  \-3  | t2  |
|2021-01-01T00:00:30Z|  19   | t2  |
|2021-01-01T00:00:40Z|  13   | t2  |
|2021-01-01T00:00:50Z|   1   | t2  |

#### Output data

|       \_time       |     \_value      |\*tag|
|--------------------|------------------|-----|
|2021-01-01T00:00:30Z|      84.375      | t1  |
|2021-01-01T00:00:40Z|73.97260273972603 | t1  |
|2021-01-01T00:00:50Z|36.672325976230894| t1  |

|       \_time       |     \_value     |\*tag|
|--------------------|-----------------|-----|
|2021-01-01T00:00:30Z|70.27027027027026| t2  |
|2021-01-01T00:00:40Z|59.42857142857142| t2  |
|2021-01-01T00:00:50Z|     40.625      | t2  |

#### Related

* [movingAverage() function](/flux/v0/stdlib/universe/movingaverage/)
* [timedMovingAverage() function](/flux/v0/stdlib/universe/timedmovingaverage/)
* [exponentialMovingAverage() function](/flux/v0/stdlib/universe/exponentialmovingaverage/)
* [InfluxQL RELATIVE\_STRENGTH\_INDEX()](/influxdb/v1/query_language/functions/#relative-strength-index)

[transformations](/flux/v0/tags/transformations/)
| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:00Z | -2 | t1 |
| 2021-01-01T00:00:10Z | 10 | t1 |
| 2021-01-01T00:00:20Z | 7 | t1 |
| 2021-01-01T00:00:30Z | 17 | t1 |
| 2021-01-01T00:00:40Z | 15 | t1 |
| 2021-01-01T00:00:50Z | 4 | t1 |

| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:00Z | 19 | t2 |
| 2021-01-01T00:00:10Z | 4 | t2 |
| 2021-01-01T00:00:20Z | -3 | t2 |
| 2021-01-01T00:00:30Z | 19 | t2 |
| 2021-01-01T00:00:40Z | 13 | t2 |
| 2021-01-01T00:00:50Z | 1 | t2 |

| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:30Z | 84.375 | t1 |
| 2021-01-01T00:00:40Z | 73.97260273972603 | t1 |
| 2021-01-01T00:00:50Z | 36.672325976230894 | t1 |

| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:30Z | 70.27027027027026 | t2 |
| 2021-01-01T00:00:40Z | 59.42857142857142 | t2 |
| 2021-01-01T00:00:50Z | 40.625 | t2 |