docs-v2/content/flux/v0/stdlib/math/log1p.md

title	description	menu	weight
math.log1p() function	`math.log1p()` returns the natural logarithm of 1 plus `x`. This operation is more accurate than `math.log(x: 1 + x)` when `x` is near zero.	flux_v0_ref name parent identifier math.log1p math math/log1p	101

math.log1p() returns the natural logarithm of 1 plus x. This operation is more accurate than math.log(x: 1 + x) when x is near zero.

Function type signature

(x: float) => float

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

Parameters

x

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

Examples

• Return the natural logarithm of values near zero
• Use math.log1p in map

Return the natural logarithm of values near zero

import "math"

math.log1p(x: 0.56)// 0.44468582126144574

Use math.log1p in map

import "math"

data
    |> map(fn: (r) => ({r with _value: math.log1p(x: r._value)}))

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Input data

_time	*tag	_value
2021-01-01T00:00:00Z	t1	-0.021800000000000003
2021-01-01T00:00:10Z	t1	0.1092
2021-01-01T00:00:20Z	t1	0.0735
2021-01-01T00:00:30Z	t1	0.1753
2021-01-01T00:00:40Z	t1	0.15230000000000002
2021-01-01T00:00:50Z	t1	0.0443

_time	*tag	_value
2021-01-01T00:00:00Z	t2	0.1985
2021-01-01T00:00:10Z	t2	0.0497
2021-01-01T00:00:20Z	t2	-0.0375
2021-01-01T00:00:30Z	t2	0.1977
2021-01-01T00:00:40Z	t2	0.1386
2021-01-01T00:00:50Z	t2	0.018600000000000002

Output data

_time	_value	*tag
2021-01-01T00:00:00Z	-0.02204113087688024	t1
2021-01-01T00:00:10Z	0.10363903475948592	t1
2021-01-01T00:00:20Z	0.07092433833669866	t1
2021-01-01T00:00:30Z	0.1615234341566714	t1
2021-01-01T00:00:40Z	0.14175994503783176	t1
2021-01-01T00:00:50Z	0.04334680450336586	t1

_time	_value	*tag
2021-01-01T00:00:00Z	0.181070774892302	t2
2021-01-01T00:00:10Z	0.048504409059614985	t2
2021-01-01T00:00:20Z	-0.03822121282019776	t2
2021-01-01T00:00:30Z	0.18040305097132403	t2
2021-01-01T00:00:40Z	0.12979943753484446	t2
2021-01-01T00:00:50Z	0.018429135468367195	t2

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