regex to match specific set of numbers or letters

Question

Working with survey data classified into various "waves", with each wave labeled either 1 - 14, or the letters "A" or "E", followed by the variable name.

For example, want to parse:

3educ > wave: 3, variable: educ
Aage > wave: A, variable: age

Tried various strings, such as

^([0-9]?|A|E)(\\w+)

to no effect. Please advise.

(Using stringr with R)

Based on your input strings, you can consider this regex [`\b([1-9]|1[0-4]|[AE])([a-z]+)\b`](https://regex101.com/r/QHKr6d/1) — Gurmanjot Singh, Jan 04 '22 at 07:35

score 1 · Answer 1 · edited Jan 04 '22 at 07:25

1

Nevermind I think I got it:

^([0-9][0-9]?|a|e)(\\w+)

edited Jan 04 '22 at 07:25

Gurmanjot Singh

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answered Jan 04 '22 at 07:14

Zhaochen He

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you regex will also select `15educ`i.e., numbersvare not restricted from 1 to 14. Moreover, [0-9] and `\w` are not mutually-exclusive. – Gurmanjot Singh Jan 04 '22 at 07:28
That's ok, as only 1-14 are present. – Zhaochen He Jan 05 '22 at 00:12

score 1 · Accepted Answer · answered Jan 04 '22 at 09:54

If you need to create a regex for a numeric range, consider using the automatic numeric range regex generator. The regex to match integer numbers from 1 to 14 is (?:[1-9]|1[0-4]).

So, you need to use

(?i)^(?P<wave>[1-9AE]|1[0-4])(?P<variable>\w+)

See the regex demo. (?i) sets the case insensitive mode on and [1-9AE] matches either a non-zero digit or A or E chars.

In R, you can use named capturing groups with namedCapture library:

x <- c("3educ","Aage","14abc","Ekajshklasjf")
library(namedCapture)
str_match_all_named(x, "(?i)^(?<wave>[1-9AE]|1[0-4])(?<variable>\\w+)")

Output:

[[1]]
     wave variable
[1,] "3"  "educ"  

[[2]]
     wave variable
[1,] "A"  "age"   

[[3]]
     wave variable
[1,] "1"  "4abc"  

[[4]]
     wave variable     
[1,] "E"  "kajshklasjf

regex to match specific set of numbers or letters

2 Answers2