---
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.
menu:
  flux_v0_ref:
    name: math.expm1
    parent: math
    identifier: math/expm1
weight: 101
---

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`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
```

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

## Parameters

### x
({{< req >}})
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)}))

```

{{< expand-wrapper >}}
{{% expand "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   |

{{% /expand %}}
{{< /expand-wrapper >}}