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

title	description	menu	weight	flux/v0/tags	introduced
sample() function	`sample()` selects a subset of the rows from each input table.	flux_v0_ref name parent identifier sample universe universe/sample	101	transformations selectors	0.7.0

sample() selects a subset of the rows from each input table.

Note: sample() drops empty tables.

Function type signature

(<-tables: stream[A], n: int, ?column: string, ?pos: int) => stream[A] where A: Record

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Parameters

n

({{< req >}}) Sample every Nth element.

pos

Position offset from the start of results where sampling begins. Default is -1 (random offset).

pos must be less than n. If pos is less than 0, a random offset is used.

column

Column to operate on.

tables

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

Examples

Sample every other result

import "sampledata"

sampledata.int()
    |> sample(n: 2, pos: 1)

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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

_time	_value	*tag
2021-01-01T00:00:10Z	10	t1
2021-01-01T00:00:30Z	17	t1
2021-01-01T00:00:50Z	4	t1

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

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