Remove strings found in vector 1, from vector 2

Question

I have these two vectors:

sample1 <- c(\".aaa\", \".aarp\", \".abb\", \".abbott\", \".abogado\")
sample2 <- c(\"try1.aarp\", \"www.tryagain.aaa\", \"25         


        

Answer 1

We can paste the 'sample1' elements together, use that as the pattern argument in gsub, replace it with ''.

gsub(paste(sample1, collapse='|'), '', sample2)
#[1] "try1"            "www.tryagain"    "255.255.255.255" "onemoretry"  

Or use mgsub

library(qdap)
mgsub(sample1, '', sample2)
#[1] "try1"            "www.tryagain"    "255.255.255.255" "onemoretry"     

Answer 2

Try this,

sample1 <- c(".aaa", ".aarp", ".abb", ".abbott", ".abogado")
sample2 <- c("try1.aarp", "www.tryagain.aaa", "255.255.255.255", "onemoretry.abb.abogado")
paste0("(",paste(sub("\\.", "\\\\.", sample1), collapse="|"),")\\b")
# [1] "(\\.aaa|\\.aarp|\\.abb|\\.abbott|\\.abogado)\\b"
gsub(paste0("(",paste(sub("\\.", "\\\\.", sample1), collapse="|"),")\\b"), "", sample2)
# [1] "try1"            "www.tryagain"    "255.255.255.255" "onemoretry" 

Explanation:

• sub("\\.", "\\\\.", sample1) escapes all the dots. Since dots are special chars in regex.

• paste(sub("\\.", "\\\\.", sample1), collapse="|") combines all the elements with | as delimiter.

• paste0("(",paste(sub("\\.", "\\\\.", sample1), collapse="|"),")\\b") creates a regex like all the elements present inside a capturing group followed by a word boundary. \\b is a much needed one here . So that it would do an exact word match.