---
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: 1314
product: Flux
version: v0
---

# math.isNaN() function

-   Flux 0.22.0+
-   View 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

```js
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 |