Change Variable Name using Regular Expression

Question

I would appreciate your help.

I want to change variables' name in R. The name of variables is "CACRAGE", "CACRAA1", etc. I want to remove "AC" in the middle, changing variables' name to "CRAGE", "CCRAA1". I've tried the following expression and it does not work. Please help me!

gsub(pattern = '^CAC([A-Z]{3,}', replacement = '^C([A-Z]{3,}', colnames(milwaukee_test), fixed = TRUE)

Thank you.

If you remove AC in CACRAA1 the result will be CRAA1 right? In that case you can match ^CAC and replace with C regex101.com/r/fy8Urk/1 — The fourth bird
– The fourth bird, Commented Aug 20, 2022 at 11:31
It sounds like you want to change strings, not variable names, correct? Those two are very different … — Konrad Rudolph
– Konrad Rudolph, Commented Aug 20, 2022 at 11:40

Allan Cameron · Accepted Answer · 2022-08-20 11:35:52Z

1

Why not just replace "CAC" with "C" if it occurs at the beginning of the name?

milwaukee_test <- data.frame(CACRAGE = 1:3, CACRAA1 = 2:4)

names(milwaukee_test) <- sub(pattern = '^CAC', "C", colnames(milwaukee_test))

milwaukee_test
#>   CRAGE CRAA1
#> 1     1     2
#> 2     2     3
#> 3     3     4

^{Created on 2022-08-20 with reprex v2.0.2}

answered Aug 20, 2022 at 11:35

Allan Cameron

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Wiktor Stribiżew · Accepted Answer · 2022-08-20 18:16:15Z

0

You can use

gsub(pattern = '^CAC(?=[A-Z]{3})', replacement = 'C', colnames(milwaukee_test), perl = TRUE)

Note

You need perl = TRUE, not fixed = TRUE, in order to use regex and lookarounds in it
^CAC(?=[A-Z]{3}) matches CAC at the start of string that is immediately followed with three uppercase ASCII letters.

answered Aug 20, 2022 at 18:16

Wiktor Stribiżew

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