docs-v2/content/flux/v0/stdlib/math/lgamma.md

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

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

Function type signature

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

{{% caption %}} For more information, see Function type signatures. {{% /caption %}}

Parameters

x

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

Examples

• Return the natural logarithm and sign of a gamma function
• Use math.lgamma in map

Return the natural logarithm and sign of a gamma function

import "math"

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

Use math.lgamma in map

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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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

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