---
title: math.expm1() function
description: math.expm1() returns e**x - 1, the base-e exponential of x minus 1. It is more accurate than math.exp(x:x) - 1 when x is near zero.
url: https://docs.influxdata.com/flux/v0/stdlib/math/expm1/
estimated_tokens: 1426
product: Flux
version: v0
---

# math.expm1() function

-   Flux 0.22.0+
-   View InfluxDB support

`math.expm1()` returns `e**x - 1`, the base-e exponential of `x` minus 1. It is more accurate than `math.exp(x:x) - 1` when `x` is near zero.

##### Function type signature

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

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

## Parameters

### x

(Required) Value to operate on.

## Examples

-   [Get more accurate base-e exponentials for values near zero](#get-more-accurate-base-e-exponentials-for-values-near-zero)
-   [Use math.expm1 in map](#use-mathexpm1-in-map)

### Get more accurate base-e exponentials for values near zero

```js
import "math"

math.expm1(x: 0.022)// 0.022243784470438233

```

### Use math.expm1 in map

```js
import "math"

data
    |> map(fn: (r) => ({r with _value: math.expm1(x: r._value)}))
```

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

View example input and output

#### Input data

| _time | *tag | _value |
| --- | --- | --- |
| 2021-01-01T00:00:00Z | t1 | -0.021800000000000003 |
| 2021-01-01T00:00:10Z | t1 | 0.1092 |
| 2021-01-01T00:00:20Z | t1 | 0.0735 |
| 2021-01-01T00:00:30Z | t1 | 0.1753 |
| 2021-01-01T00:00:40Z | t1 | 0.15230000000000002 |
| 2021-01-01T00:00:50Z | t1 | 0.0443 |

| _time | *tag | _value |
| --- | --- | --- |
| 2021-01-01T00:00:00Z | t2 | 0.1985 |
| 2021-01-01T00:00:10Z | t2 | 0.0497 |
| 2021-01-01T00:00:20Z | t2 | -0.0375 |
| 2021-01-01T00:00:30Z | t2 | 0.1977 |
| 2021-01-01T00:00:40Z | t2 | 0.1386 |
| 2021-01-01T00:00:50Z | t2 | 0.018600000000000002 |

#### Output data

| _time | _value | *tag |
| --- | --- | --- |
| 2021-01-01T00:00:00Z | -0.02156409733567063 | t1 |
| 2021-01-01T00:00:10Z | 0.11538540511625006 | t1 |
| 2021-01-01T00:00:20Z | 0.07626853667189179 | t1 |
| 2021-01-01T00:00:30Z | 0.1916036440887826 | t1 |
| 2021-01-01T00:00:40Z | 0.16450953689549175 | t1 |
| 2021-01-01T00:00:50Z | 0.045295896623819054 | t1 |

| _time | _value | *tag |
| --- | --- | --- |
| 2021-01-01T00:00:00Z | 0.21957202741425103 | t2 |
| 2021-01-01T00:00:10Z | 0.05095576234958021 | t2 |
| 2021-01-01T00:00:20Z | -0.03680558227917823 | t2 |
| 2021-01-01T00:00:30Z | 0.21859675995131905 | t2 |
| 2021-01-01T00:00:40Z | 0.14866454228127554 | t2 |
| 2021-01-01T00:00:50Z | 0.018774057481622756 | t2 |