---
title: math.isInf() function
description: >
  `math.isInf()` reports whether `f` is an infinity, according to `sign`.
menu:
  flux_v0_ref:
    name: math.isInf
    parent: math
    identifier: math/isInf
weight: 101
---

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`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
```

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

## Parameters

### f
({{< req >}})
is the value used in the evaluation.



### sign
({{< req >}})
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)}))

```

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{{% expand "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   |

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{{< /expand-wrapper >}}