---
title: math.isNaN() function
description: math.isNaN() reports whether f is an IEEE 754 “not-a-number” value.
url: https://docs.influxdata.com/flux/v0/stdlib/math/isnan/
estimated_tokens: 790
product: Flux
version: v0
publisher: InfluxData
canonical: https://docs.influxdata.com/flux/v0/stdlib/math/isnan/
date: '2024-04-08T16:01:02-06:00'
lastmod: '2024-04-08T16:01:02-06:00'
---

* Flux 0.22.0+

InfluxDB support

`math.isNaN()` reports whether `f` is an IEEE 754 “not-a-number” value.

##### Function type signature

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

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

## Parameters

### f

(Required)
Value to operate on.

## Examples

* [Check if a value is a NaN float value](#check-if-a-value-is-a-nan-float-value)
* [Use math.isNaN in map](#use-mathisnan-in-map)

### Check if a value is a NaN float value

```
import "math"

math.isNaN(f: 12.345)// false

```

### Use math.isNaN in map

```js
import "math"

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

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

#### Output data

|       \_time       |\_value|\*tag|
|--------------------|-------|-----|
|2021-01-01T00:00:00Z| false | 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| false | t2  |
|2021-01-01T00:00:30Z| false | t2  |
|2021-01-01T00:00:40Z| true  | t2  |
|2021-01-01T00:00:50Z| false | t2  |
| _time | *tag | _value |
| --- | --- | --- |
| _time | *tag | _value |
| 2021-01-01T00:00:00Z | t1 | -2.18 |
| 2021-01-01T00:00:10Z | t1 | NaN |
| 2021-01-01T00:00:20Z | t1 | 7.35 |
| 2021-01-01T00:00:30Z | t1 | NaN |
| 2021-01-01T00:00:40Z | t1 | NaN |
| 2021-01-01T00:00:50Z | t1 | 4.43 |

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

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