Remove all dots but first in a string using R

Question

I have some errors in some numbers showing numbers like "59.34343.23". I know the first dot is correct but the second one (or any after the first) should be remove. How can I remove those?

I tried using gsub in R:

gsub("(?<=\\..*)\\.", "", "59.34343.23", perl=T)

or

gsub("(?<!^[^.]*)\\.", "", "59.34343.23", perl=T)

However it gets the following error "invalid regular expression". But I have been trying the same code in a regex tester and it works. What is my mistake here?

Answer 1

You can use

gsub("^([^.]*\\.)|\\.", "\\1", "59.34343.23")
gsub("^([^.]*\\.)|\\.", "\\1", "59.34343.23", perl=TRUE)

See the R demo online and the regex demo.

Details:

• ^([^.]*\.) - Capturing group 1 (referred to as \1 from the replacement pattern): any zero or more chars from the start of string and then a . char (the first in the string)
• | - or
• \. - any other dot in the string.

Since the replacement, \1, refers to Group 1, and Group 1 only contains a value after the text before and including the first dot is matched, the replacement is either this part of text, or empty string (i.e. the second and all subsequent occurrences of dots are removed).