docs-v2/content/flux/v0.x/stdlib/universe/first.md

title	description	menu	weight	flux/v0.x/tags	introduced
first() function	`first()` returns the first non-null record from each input table.	flux_0_x_ref name parent identifier first universe universe/first	101	transformations selectors	0.7.0

first() returns the first non-null record from each input table.

Note: first() drops empty tables.

Function type signature

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

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

Parameters

column

Column to operate on. Default is _value.

tables

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

Examples

Return the first row in each input table

import "sampledata"

sampledata.int()
    |> first()

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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
2021-01-01T00:00:00Z	-2	t1

_time	_value	*tag
2021-01-01T00:00:00Z	19	t2

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