---
title: math.log1p() function
description: >
  `math.log1p()` returns the natural logarithm of 1 plus `x`.
  This operation is more accurate than `math.log(x: 1 + x)` when `x` is
  near zero.
menu:
  flux_v0_ref:
    name: math.log1p
    parent: math
    identifier: math/log1p
weight: 101
---

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`math.log1p()` returns the natural logarithm of 1 plus `x`.
This operation is more accurate than `math.log(x: 1 + x)` 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

- [Return the natural logarithm of values near zero](#return-the-natural-logarithm-of-values-near-zero)
- [Use math.log1p in map](#use-mathlog1p-in-map)

### Return the natural logarithm of values near zero

```js
import "math"

math.log1p(x: 0.56)// 0.44468582126144574


```


### Use math.log1p in map

```js
import "math"

data
    |> map(fn: (r) => ({r with _value: math.log1p(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 | -0.02204113087688024 | t1   |
| 2021-01-01T00:00:10Z | 0.10363903475948592  | t1   |
| 2021-01-01T00:00:20Z | 0.07092433833669866  | t1   |
| 2021-01-01T00:00:30Z | 0.1615234341566714   | t1   |
| 2021-01-01T00:00:40Z | 0.14175994503783176  | t1   |
| 2021-01-01T00:00:50Z | 0.04334680450336586  | t1   |

| _time                | _value               | *tag |
| -------------------- | -------------------- | ---- |
| 2021-01-01T00:00:00Z | 0.181070774892302    | t2   |
| 2021-01-01T00:00:10Z | 0.048504409059614985 | t2   |
| 2021-01-01T00:00:20Z | -0.03822121282019776 | t2   |
| 2021-01-01T00:00:30Z | 0.18040305097132403  | t2   |
| 2021-01-01T00:00:40Z | 0.12979943753484446  | t2   |
| 2021-01-01T00:00:50Z | 0.018429135468367195 | t2   |

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