docs-v2/content/flux/v0/stdlib/strings/isletter.md

title	description	menu	weight
strings.isLetter() function	`strings.isLetter()` tests if a single character string is a letter (a-z, A-Z).	flux_v0_ref name parent identifier strings.isLetter strings strings/isLetter	101

strings.isLetter() tests if a single character string is a letter (a-z, A-Z).

Function type signature

(v: string) => bool

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

Parameters

v

({{< req >}}) Single-character string to test.

Examples

Filter by columns with digits as values

import "strings"

data
    |> filter(fn: (r) => strings.isLetter(v: r._value))

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Input data

_time	_value	*tag
2021-01-01T00:00:00Z	s	t1
2021-01-01T00:00:10Z	n	t1
2021-01-01T00:00:20Z	4	t1
2021-01-01T00:00:30Z	4	t1
2021-01-01T00:00:40Z	e	t1
2021-01-01T00:00:50Z	y	t1

_time	_value	*tag
2021-01-01T00:00:00Z	a	t2
2021-01-01T00:00:10Z	p	t2
2021-01-01T00:00:20Z	4	t2
2021-01-01T00:00:30Z	t	t2
2021-01-01T00:00:40Z	7	t2
2021-01-01T00:00:50Z	v	t2

Output data

_time	_value	*tag
2021-01-01T00:00:00Z	s	t1
2021-01-01T00:00:10Z	n	t1
2021-01-01T00:00:40Z	e	t1
2021-01-01T00:00:50Z	y	t1

_time	_value	*tag
2021-01-01T00:00:00Z	a	t2
2021-01-01T00:00:10Z	p	t2
2021-01-01T00:00:30Z	t	t2
2021-01-01T00:00:50Z	v	t2

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