docs-v2/content/flux/v0/stdlib/math/expm1.md

title	description	menu	weight
math.expm1() function	`math.expm1()` returns `e**x - 1`, the base-e exponential of `x` minus 1. It is more accurate than `math.exp(x:x) - 1` when `x` is near zero.	flux_v0_ref name parent identifier math.expm1 math math/expm1	101

math.expm1() returns e**x - 1, the base-e exponential of x minus 1. It is more accurate than math.exp(x:x) - 1 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

• Get more accurate base-e exponentials for values near zero
• Use math.expm1 in map

Get more accurate base-e exponentials for values near zero

import "math"

math.expm1(x: 0.022)// 0.022243784470438233

Use math.expm1 in map

import "math"

data
    |> map(fn: (r) => ({r with _value: math.expm1(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	-0.02156409733567063	t1
2021-01-01T00:00:10Z	0.11538540511625006	t1
2021-01-01T00:00:20Z	0.07626853667189179	t1
2021-01-01T00:00:30Z	0.1916036440887826	t1
2021-01-01T00:00:40Z	0.16450953689549175	t1
2021-01-01T00:00:50Z	0.045295896623819054	t1

_time	_value	*tag
2021-01-01T00:00:00Z	0.21957202741425103	t2
2021-01-01T00:00:10Z	0.05095576234958021	t2
2021-01-01T00:00:20Z	-0.03680558227917823	t2
2021-01-01T00:00:30Z	0.21859675995131905	t2
2021-01-01T00:00:40Z	0.14866454228127554	t2
2021-01-01T00:00:50Z	0.018774057481622756	t2

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