---
title: math.y1() function
description: math.y1() returns the order-one Bessel function of the second kind.
url: https://docs.influxdata.com/flux/v0/stdlib/math/y1/
estimated_tokens: 1407
product: Flux
version: v0
---

# math.y1() function

-   Flux 0.22.0+
-   View InfluxDB support

`math.y1()` returns the order-one Bessel function of the second kind.

##### Function type signature

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

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

## Parameters

### x

(Required) Value to operate on.

## Examples

-   [Return the order-one Bessel function of a value](#return-the-order-one-bessel-function-of-a-value)
-   [Use math.y1 in map](#use-mathy1-in-map)

### Return the order-one Bessel function of a value

```js
import "math"

math.y1(x: 3.14)// 0.35853138083924085

```

### Use math.y1 in map

```js
import "math"
import "sampledata"

sampledata.float()
    |> map(fn: (r) => ({r with _value: math.y1(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 | 10.92 |
| 2021-01-01T00:00:20Z | t1 | 7.35 |
| 2021-01-01T00:00:30Z | t1 | 17.53 |
| 2021-01-01T00:00:40Z | t1 | 15.23 |
| 2021-01-01T00:00:50Z | t1 | 4.43 |

| _time | *tag | _value |
| --- | --- | --- |
| 2021-01-01T00:00:00Z | t2 | 19.85 |
| 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 | 13.86 |
| 2021-01-01T00:00:50Z | t2 | 1.86 |

#### Output data

| _time | _value | *tag |
| --- | --- | --- |
| 2021-01-01T00:00:00Z | NaN | t1 |
| 2021-01-01T00:00:10Z | 0.17792152059156155 | t1 |
| 2021-01-01T00:00:20Z | -0.279177585983904 | t1 |
| 2021-01-01T00:00:30Z | 0.09355230538878848 | t1 |
| 2021-01-01T00:00:40Z | 0.06669358775929306 | t1 |
| 2021-01-01T00:00:50Z | 0.318734411734819 | t1 |

| _time | _value | *tag |
| --- | --- | --- |
| 2021-01-01T00:00:00Z | -0.17429072159140693 | t2 |
| 2021-01-01T00:00:10Z | 0.15797094698544048 | t2 |
| 2021-01-01T00:00:20Z | NaN | t2 |
| 2021-01-01T00:00:30Z | -0.17740857181789169 | t2 |
| 2021-01-01T00:00:40Z | -0.18452518993372807 | t2 |
| 2021-01-01T00:00:50Z | -0.18788912184316153 | t2 |