---
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: 1402
product: Flux
version: v0
---

# math.log2() function

-   Flux 0.22.0+
-   View 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

```js
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 |