---
title: math.signbit() function
description: math.signbit() reports whether x is negative or negative zero.
url: https://docs.influxdata.com/flux/v0/stdlib/math/signbit/
estimated_tokens: 1309
product: Flux
version: v0
---

# math.signbit() function

-   Flux 0.22.0+
-   View InfluxDB support

`math.signbit()` reports whether `x` is negative or negative zero.

##### Function type signature

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

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

## Parameters

### x

(Required) Value to evaluate.

## Examples

-   [Test if a value is negative](#test-if-a-value-is-negative)
-   [Use math.signbit in map](#use-mathsignbit-in-map)

### Test if a value is negative

```js
import "math"

math.signbit(x: -1.2)// true

```

### Use math.signbit in map

```js
import "math"

data
    |> map(fn: (r) => ({r with _value: math.signbit(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 | -0 |
| 2021-01-01T00:00:20Z | t1 | 7.35 |
| 2021-01-01T00:00:30Z | t1 | -0 |
| 2021-01-01T00:00:40Z | t1 | -0 |
| 2021-01-01T00:00:50Z | t1 | 4.43 |

| _time | *tag | _value |
| --- | --- | --- |
| 2021-01-01T00:00:00Z | t2 | -0 |
| 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 | -0 |
| 2021-01-01T00:00:50Z | t2 | 1.86 |

#### Output data

| _time | _value | *tag |
| --- | --- | --- |
| 2021-01-01T00:00:00Z | true | t1 |
| 2021-01-01T00:00:10Z | true | t1 |
| 2021-01-01T00:00:20Z | false | t1 |
| 2021-01-01T00:00:30Z | true | t1 |
| 2021-01-01T00:00:40Z | true | t1 |
| 2021-01-01T00:00:50Z | false | t1 |

| _time | _value | *tag |
| --- | --- | --- |
| 2021-01-01T00:00:00Z | true | t2 |
| 2021-01-01T00:00:10Z | false | t2 |
| 2021-01-01T00:00:20Z | true | t2 |
| 2021-01-01T00:00:30Z | false | t2 |
| 2021-01-01T00:00:40Z | true | t2 |
| 2021-01-01T00:00:50Z | false | t2 |