Count occurrences of a substring in a string

Question

I'm trying to count the number of times a string, say AAA occurs in a longer string, say AAAA. The answer in this case is clearly 2:

• AAAA
• AAAA

None of these work as I would expect:

stringi::stri_count(str = "AAAA", regex = "AAA")
[1]

stringr::str_count(string = "AAAA", pattern = "AAA")
[1]

stringr::str_extract_all("AAAA", "AAA", simplify = T)
     [,1]
[1,] "AAA"

What am I doing wrong here?

Answer 1

You could use a look ahead positive regex (?=) to count the occurrence of the substring like this:

stringi::stri_count(str = "AAAA", regex = "(?=AAA)")
#> [1] 2

^{Created on 2023-10-03 with reprex v2.0.2}