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

title	description	menu	weight	flux/v0/tags	introduced
drop() function	`drop()` removes specified columns from a table.	flux_v0_ref name parent identifier drop universe universe/drop	101	transformations	0.7.0

drop() removes specified columns from a table.

Columns are specified either through a list or a predicate function. When a dropped column is part of the group key, it is removed from the key. If a specified column is not present in a table, the function returns an error.

Function type signature

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

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

Parameters

columns

List of columns to remove from input tables. Mutually exclusive with fn.

fn

Predicate function with a column parameter that returns a boolean value indicating whether or not the column should be removed from input tables. Mutually exclusive with columns.

tables

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

Examples

• Drop a list of columns
• Drop columns matching a predicate

Drop a list of columns

import "sampledata"

sampledata.int()
    |> drop(columns: ["_time", "tag"])

{{< 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

_value
-2
10
7
17
15
4
19
4
-3
19
13
1

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

Drop columns matching a predicate

import "sampledata"

sampledata.int()
    |> drop(fn: (column) => column =~ /^t/)

{{< 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
2021-01-01T00:00:00Z	-2
2021-01-01T00:00:10Z	10
2021-01-01T00:00:20Z	7
2021-01-01T00:00:30Z	17
2021-01-01T00:00:40Z	15
2021-01-01T00:00:50Z	4
2021-01-01T00:00:00Z	19
2021-01-01T00:00:10Z	4
2021-01-01T00:00:20Z	-3
2021-01-01T00:00:30Z	19
2021-01-01T00:00:40Z	13
2021-01-01T00:00:50Z	1

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