---
title: math.log2() function
description: math.log2() is a function returns the binary logarithm of x.
url: https://docs.influxdata.com/flux/v0/stdlib/math/log2/
estimated_tokens: 879
product: Flux
version: v0
publisher: InfluxData
canonical: https://docs.influxdata.com/flux/v0/stdlib/math/log2/
date: '2024-04-08T16:01:02-06:00'
lastmod: '2024-04-08T16:01:02-06:00'
---

* Flux 0.22.0+

InfluxDB support

`math.log2()` is a function returns the binary logarithm of `x`.

##### Function type signature

```js
(x: float) => float
```

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

## Parameters

### x

(Required)
the value used in the operation.

## Examples

* [Return the binary logarithm of a value](#return-the-binary-logarithm-of-a-value)
* [Use math.log2 in map](#use-mathlog2-in-map)

### Return the binary logarithm of a value

```
import "math"

math.log2(x: 3.14)// 1.6507645591169022

```

### Use math.log2 in map

```js
import "sampledata"
import "math"

sampledata.float()
    |> map(fn: (r) => ({r with _value: math.log2(x: r._value)}))
```

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

View example input and output

#### Input data

|       \_time       |\*tag|\_value|
|--------------------|-----|-------|
|2021-01-01T00:00:00Z| t1  |\-2.18 |
|2021-01-01T00:00:10Z| t1  | 10.92 |
|2021-01-01T00:00:20Z| t1  | 7.35  |
|2021-01-01T00:00:30Z| t1  | 17.53 |
|2021-01-01T00:00:40Z| t1  | 15.23 |
|2021-01-01T00:00:50Z| t1  | 4.43  |

|       \_time       |\*tag|\_value|
|--------------------|-----|-------|
|2021-01-01T00:00:00Z| t2  | 19.85 |
|2021-01-01T00:00:10Z| t2  | 4.97  |
|2021-01-01T00:00:20Z| t2  |\-3.75 |
|2021-01-01T00:00:30Z| t2  | 19.77 |
|2021-01-01T00:00:40Z| t2  | 13.86 |
|2021-01-01T00:00:50Z| t2  | 1.86  |

#### Output data

|       \_time       |     \_value      |\*tag|
|--------------------|------------------|-----|
|2021-01-01T00:00:00Z|       NaN        | t1  |
|2021-01-01T00:00:10Z|3.4489009511451276| t1  |
|2021-01-01T00:00:20Z|2.877744249949002 | t1  |
|2021-01-01T00:00:30Z|4.131754090984813 | t1  |
|2021-01-01T00:00:40Z|3.9288440367125674| t1  |
|2021-01-01T00:00:50Z|2.1473066987802936| t1  |

|       \_time       |     \_value      |\*tag|
|--------------------|------------------|-----|
|2021-01-01T00:00:00Z|4.3110671022555955| t2  |
|2021-01-01T00:00:10Z|2.3132458517875616| t2  |
|2021-01-01T00:00:20Z|       NaN        | t2  |
|2021-01-01T00:00:30Z|4.305240965954483 | t2  |
|2021-01-01T00:00:40Z|3.792855352362489 | t2  |
|2021-01-01T00:00:50Z|0.8953026213333067| t2  |
| _time | *tag | _value |
| --- | --- | --- |
| _time | *tag | _value |
| 2021-01-01T00:00:00Z | t1 | -2.18 |
| 2021-01-01T00:00:10Z | t1 | 10.92 |
| 2021-01-01T00:00:20Z | t1 | 7.35 |
| 2021-01-01T00:00:30Z | t1 | 17.53 |
| 2021-01-01T00:00:40Z | t1 | 15.23 |
| 2021-01-01T00:00:50Z | t1 | 4.43 |

| _time | *tag | _value |
| --- | --- | --- |
| _time | *tag | _value |
| 2021-01-01T00:00:00Z | t2 | 19.85 |
| 2021-01-01T00:00:10Z | t2 | 4.97 |
| 2021-01-01T00:00:20Z | t2 | -3.75 |
| 2021-01-01T00:00:30Z | t2 | 19.77 |
| 2021-01-01T00:00:40Z | t2 | 13.86 |
| 2021-01-01T00:00:50Z | t2 | 1.86 |

| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:00Z | NaN | t1 |
| 2021-01-01T00:00:10Z | 3.4489009511451276 | t1 |
| 2021-01-01T00:00:20Z | 2.877744249949002 | t1 |
| 2021-01-01T00:00:30Z | 4.131754090984813 | t1 |
| 2021-01-01T00:00:40Z | 3.9288440367125674 | t1 |
| 2021-01-01T00:00:50Z | 2.1473066987802936 | t1 |

| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:00Z | 4.3110671022555955 | t2 |
| 2021-01-01T00:00:10Z | 2.3132458517875616 | t2 |
| 2021-01-01T00:00:20Z | NaN | t2 |
| 2021-01-01T00:00:30Z | 4.305240965954483 | t2 |
| 2021-01-01T00:00:40Z | 3.792855352362489 | t2 |
| 2021-01-01T00:00:50Z | 0.8953026213333067 | t2 |