Estrarre tutte le parole tra due parole specifiche in un vettore di caratteri

Question

Esiste un metodo più efficiente? Come posso fare questo senza stringr?

txt <- "I want to extract the words between this and that, this goes with that, this is a long way from that" 

library(stringr) 
w_start <- "this" 
w_end <- "that" 
pattern <- paste0(w_start, "(.*?)", w_end) 
wordsbetween <- unlist(str_extract_all(txt, pattern)) 
gsub("^\\s+|\\s+$", "", str_sub(wordsbetween, nchar(w_start)+1, -nchar(w_end)-1)) 
[1] "and"    "goes with"   "is a long way from" 

Answer 1

Questo è un approccio che uso nel qdap:

Utilizzando qdap:

library(qdap) 
genXtract(txt, "this", "that") 

## > genXtract(txt, "this", "that") 
##   this : that1   this : that2   this : that3 
##    " and "   " goes with " " is a long way from " 

Senza un add on pacchetto:

regmatches(txt, gregexpr("(?<=this).*?(?=that)", txt, perl=TRUE)) 

## > regmatches(txt, gregexpr("(?<=this).*?(?=that)", txt, perl=TRUE)) 
## [[1]] 
## [1] " and "    " goes with "   " is a long way from " 

Answer 2

Ecco un altro ruvido provare a utilizzare strsplit, sebbene possa essere ulteriormente perfezionato:

txtspl <- unlist(strsplit(gsub("[[:punct:]]","",txt),"this|that")) 
txtspl[txtspl!=" "][-1] 

#[1] " and "    " goes with "   " is a long way from "