[R] gsub issue with consecutive pattern finds

[Iris Simmons]

Hi Iago,


This is not a bug. It is expected. Patterns may not overlap. However, there
is a way to get the result you want using perl:

```R
gsub("([aeiouAEIOU])(?=[aeiouAEIOU])", "\\1_", "aerioue", perl = TRUE)
```

The specific change I made is called a positive lookahead, you can read
more about it here:

https://www.regular-expressions.info/lookaround.html

It's a way to check for a piece of text without consuming it in the match.

Also, since you don't care about character case, it might be more legible
to add ignore.case = TRUE and remove the upper case characters:

```R
gsub("([aeiou])(?=[aeiou])", "\\1_", "aerioue", perl = TRUE, ignore.case =
TRUE)

## or

gsub("(?i)([aeiou])(?=[aeiou])", "\\1_", "aerioue", perl = TRUE)
```

I hope this helps!


On Fri, Mar 1, 2024, 06:37 Iago Giné Vázquez <iago.gine using sjd.es> wrote:

> Hi all,
>
> I tested next command:
>
> gsub("([aeiouAEIOU])([aeiouAEIOU])", "\\1_\\2", "aerioue")
>
> with the following output:
>
> [1] "a_eri_ou_e"
>
> So, there are two consecutive vowels where an underscore is not added.
>
> May it be a bug? Is it expected (bug or not)? Is there any chance to get
> what I want (an underscore between each pair of consecutive vowels)?
>
>
> Thank you!
>
> Best regards,
>
> Iago
>
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>
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