docs-v2/content/flux/v0/stdlib/math/log2.md

title	description	menu	weight
math.log2() function	`math.log2()` is a function returns the binary logarithm of `x`.	flux_v0_ref name parent identifier math.log2 math math/log2	101

math.log2() is a function returns the binary logarithm of x.

Function type signature

(x: float) => float

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

Parameters

x

({{< req >}}) the value used in the operation.

Examples

• Return the binary logarithm of a value
• Use math.log2 in map

Return the binary logarithm of a value

import "math"

math.log2(x: 3.14)// 1.6507645591169022

Use math.log2 in map

import "sampledata"
import "math"

sampledata.float()
    |> map(fn: (r) => ({r with _value: math.log2(x: r._value)}))

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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	*tag
2021-01-01T00:00:00Z	NaN	t1
2021-01-01T00:00:10Z	3.4489009511451276	t1
2021-01-01T00:00:20Z	2.877744249949002	t1
2021-01-01T00:00:30Z	4.131754090984813	t1
2021-01-01T00:00:40Z	3.9288440367125674	t1
2021-01-01T00:00:50Z	2.1473066987802936	t1

_time	_value	*tag
2021-01-01T00:00:00Z	4.3110671022555955	t2
2021-01-01T00:00:10Z	2.3132458517875616	t2
2021-01-01T00:00:20Z	NaN	t2
2021-01-01T00:00:30Z	4.305240965954483	t2
2021-01-01T00:00:40Z	3.792855352362489	t2
2021-01-01T00:00:50Z	0.8953026213333067	t2

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