---
title: math.lgamma() function
description: >
  `math.lgamma()` returns the natural logarithm and sign (-1 or +1) of `math.gamma(x:x)`.
menu:
  flux_v0_ref:
    name: math.lgamma
    parent: math
    identifier: math/lgamma
weight: 101
---

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`math.lgamma()` returns the natural logarithm and sign (-1 or +1) of `math.gamma(x:x)`.



##### Function type signature

```js
(x: float) => {sign: int, lgamma: float}
```

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

## Parameters

### x
({{< req >}})
Value to operate on.




## Examples

- [Return the natural logarithm and sign of a gamma function](#return-the-natural-logarithm-and-sign-of-a-gamma-function)
- [Use math.lgamma in map](#use-mathlgamma-in-map)

### Return the natural logarithm and sign of a gamma function

```js
import "math"

math.lgamma(x: 3.14)// {lgamma: 0.8261387047770286, sign: 1}


```


### Use math.lgamma in map

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

sampledata.float()
    |> map(
        fn: (r) => {
            result = math.lgamma(x: r._value)

            return {r with lgamma: result.lgamma, sign: result.sign}
        },
    )

```

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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   | 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  | lgamma             | sign  | *tag |
| -------------------- | ------- | ------------------ | ----- | ---- |
| 2021-01-01T00:00:00Z | -2.18   | 0.9031727084064437 | -1    | t1   |
| 2021-01-01T00:00:10Z | 10.92   | 14.916577673425685 | 1     | t1   |
| 2021-01-01T00:00:20Z | 7.35    | 7.243966588004043  | 1     | t1   |
| 2021-01-01T00:00:30Z | 17.53   | 32.16614206633506  | 1     | t1   |
| 2021-01-01T00:00:40Z | 15.23   | 25.808134773211734 | 1     | t1   |
| 2021-01-01T00:00:50Z | 4.43    | 2.3571285321490905 | 1     | t1   |

| _time                | _value  | lgamma                | sign  | *tag |
| -------------------- | ------- | --------------------- | ----- | ---- |
| 2021-01-01T00:00:00Z | 19.85   | 38.8948838691485      | 1     | t2   |
| 2021-01-01T00:00:10Z | 4.97    | 3.132970115904918     | 1     | t2   |
| 2021-01-01T00:00:20Z | -3.75   | -1.3172679424463634   | 1     | t2   |
| 2021-01-01T00:00:30Z | 19.77   | 38.65802514327764     | 1     | t2   |
| 2021-01-01T00:00:40Z | 13.86   | 22.188483434123324    | 1     | t2   |
| 2021-01-01T00:00:50Z | 1.86    | -0.052676311706898016 | 1     | t2   |

{{% /expand %}}
{{< /expand-wrapper >}}