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

title	description	menu	weight	flux/v0/tags	introduced
tail() function	`tail()` limits each output table to the last `n` rows.	flux_v0_ref name parent identifier tail universe universe/tail	101	transformations	0.39.0

tail() limits each output table to the last n rows.

tail() produces one output table for each input table. Each output table contains the last n records before the offset. If the input table has less than offset + n records, tail() outputs all records before the offset.

Function type signature

(<-tables: stream[A], n: int, ?offset: int) => stream[A]

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

Parameters

n

({{< req >}}) Maximum number of rows to output.

offset

Number of records to skip at the end of a table table before limiting to n. Default is 0.

tables

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

Examples

• Output the last three rows in each input table
• Output the last three rows before the last row in each input table

Output the last three rows in each input table

import "sampledata"

sampledata.int()
    |> tail(n: 3)

{{< expand-wrapper >}} {{% expand "View example input and output" %}}

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
2021-01-01T00:00:30Z	17	t1
2021-01-01T00:00:40Z	15	t1
2021-01-01T00:00:50Z	4	t1

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

{{% /expand %}} {{< /expand-wrapper >}}

Output the last three rows before the last row in each input table

import "sampledata"

sampledata.int()
    |> tail(n: 3, offset: 1)

{{< expand-wrapper >}} {{% expand "View example input and output" %}}

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
2021-01-01T00:00:20Z	7	t1
2021-01-01T00:00:30Z	17	t1
2021-01-01T00:00:40Z	15	t1

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

{{% /expand %}} {{< /expand-wrapper >}}