docs-v2/content/flux/v0/stdlib/universe/stddev.md

title	description	menu	weight	flux/v0/tags	introduced
stddev() function	`stddev()` returns the standard deviation of non-null values in a specified column.	flux_v0_ref name parent identifier stddev universe universe/stddev	101	transformations aggregates	0.7.0

stddev() returns the standard deviation of non-null values in a specified column.

Function type signature

(<-tables: stream[A], ?column: string, ?mode: string) => stream[B] where A: Record, B: Record

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Parameters

column

Column to operate on. Default is _value.

mode

Standard deviation mode or type of standard deviation to calculate. Default is sample.

Available modes:

• sample: Calculate the sample standard deviation where the data is considered part of a larger population.
• population: Calculate the population standard deviation where the data is considered a population of its own.

tables

Input data. Default is piped-forward data (<-).

Examples

Return the standard deviation of values in each table

import "sampledata"

sampledata.int()
    |> stddev()

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Input data

_time	_value	*tag
2021-01-01T00:00:00Z	-2	t1
2021-01-01T00:00:10Z	10	t1
2021-01-01T00:00:20Z	7	t1
2021-01-01T00:00:30Z	17	t1
2021-01-01T00:00:40Z	15	t1
2021-01-01T00:00:50Z	4	t1

_time	_value	*tag
2021-01-01T00:00:00Z	19	t2
2021-01-01T00:00:10Z	4	t2
2021-01-01T00:00:20Z	-3	t2
2021-01-01T00:00:30Z	19	t2
2021-01-01T00:00:40Z	13	t2
2021-01-01T00:00:50Z	1	t2

Output data

*tag	_value
t1	7.063993204979744

*tag	_value
t2	9.474527252938094

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