在 R 中使用模糊 LR 模式提取字符串

Question

I am struggling for long time.

I manage to extract everything between my Right and Left patterns in a string as you can see in the following example.

library(tidyverse)

data=c("everything will be ok one day")

str_extract(string = data, pattern = "(?<=thing).*(?=ok one)")
#> [1] " will be "

^{Created on 2022-01-26 by the reprex package (v2.0.1)}

As you notice in the code, I extract everything between "thing" and "ok one".

I need to incorporate the possibility of mismatches inside these patterns. I want to allow a maximum of two mismatches and consider indels and insertions.

---

Example

for example one mismatch that I want to account for is the insertion of letter "s" in everything

dat.1=c("everythings will be ok one day")

I would like in this case to be able to extract the the phrase

will be 

---

PS: This is just a simplified example. My actual data does not contain gaps, and it's complicated. I am looking forward to receiving your help and guidance.

Answer 1

One way is to use fuzzy matching of strings, relying, for instance, on package stringdist and computing, for each delimiter string ( thing and ok , in your example), the respective matching score (that is what the function maxsim does below).

library(tidyverse)
library(stringdist)

dat.1=c("everythings will be ok one day")

maxsim <- function(df, delim)
{
  df %>% 
    str_split(" ") %>% unlist %>% 
    map(~ stringsim(delim,.x)) %>% 
    which.max
} 

dat.1 %>% 
  str_split(" ") %>% unlist %>% 
  .[ (maxsim(dat.1,"thing") + 1) : (maxsim(dat.1,"ok") - 1) ] %>% 
  str_c(collapse = " ")

#> [1] "will be"