CODEWITHSUNDEEP
rregex
mlinegar
mlinegar

Reputation: 1399

Grep a variable and store the result in a vector in R

I have a list of txt files stored in A.path that I would like to use grep on to find the year associated with that file, and save this year to a vector. However, as some of these txt files have multiple years in their text, I would only like to store the first year. How can I do this?

I've done similar things using lapply, and this is how I began approaching this problem:

lapply(A.path, function(i){
j <- paste0(scan(i, what = character(), comment.char='', quote=NULL),  collapse = " ")
year <- vector()
year[i] <- grep('[0-9][0-9][0-9][0-9]', j)
})

grep probably isn't the right function to use, as this returns the entirety of j for each i. What is the right function to use here?

Upvotes: 5

Views: 1198

Answers (1)

Rorschach
Rorschach

Reputation: 32456

Converting comment to answer, you can use gsub with \\1 to extract the value of the first match (ie. the text matched between () in the regex)

gsub(".*?([0-9]{4}).*", "\\1", j)

Upvotes: 5

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