---
title: math.isInf() function
description: math.isInf() reports whether f is an infinity, according to sign.
url: https://docs.influxdata.com/flux/v0/stdlib/math/isinf/
estimated_tokens: 1494
product: Flux
version: v0
---

# math.isInf() function

-   Flux 0.22.0+
-   View InfluxDB support

`math.isInf()` reports whether `f` is an infinity, according to `sign`.

If `sign > 0`, math.isInf reports whether `f` is positive infinity. If `sign < 0`, math.isInf reports whether `f` is negative infinity. If `sign == 0`, math.isInf reports whether `f` is either infinity.

##### Function type signature

```js
(f: float, sign: int) => bool
```

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

## Parameters

### f

(Required) is the value used in the evaluation.

### sign

(Required) is the sign used in the evaluation.

## Examples

-   [Test if a value is an infinity value](#test-if-a-value-is-an-infinity-value)
-   [Use math.isInf in map](#use-mathisinf-in-map)

### Test if a value is an infinity value

```js
import "math"

math.isInf(f: 2.12, sign: 3)// false

```

### Use math.isInf in map

```js
import "math"

data
    |> map(fn: (r) => ({r with _value: math.isInf(f: r._value, sign: 1)}))
```

[](#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 | +Inf |
| 2021-01-01T00:00:20Z | t1 | 7.35 |
| 2021-01-01T00:00:30Z | t1 | +Inf |
| 2021-01-01T00:00:40Z | t1 | +Inf |
| 2021-01-01T00:00:50Z | t1 | 4.43 |

| _time | *tag | _value |
| --- | --- | --- |
| 2021-01-01T00:00:00Z | t2 | +Inf |
| 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 | +Inf |
| 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 |