CODEWITHSUNDEEP
rstringextract
Prabha
Prabha

Reputation: 21

Is there an R function to extract all numbers followed by specific pattern?

I am working R. I want to extract all numbers between the last blank space and a string pattern ("-APPLE") in a vector. The numbers can be of variable length. 

test_string = c("ABC 2-APPLE", "123 25-APPLE", "DEF GHI 567-APPLE", "ORANGE")

Expected Result set should be a vector as in c(2, 25, 567, NA)

Upvotes: 0

Views: 197

Answers (2)

ayeh
ayeh

Reputation: 68

you can use the "rebus" package, which is very user-friendly in creating the regex patterns you need. 

library(rebus)
## adjust the lo and hi arguments of dgt() based on your text

rx <- lookbehind(SPACE) %R% dgt(1,5) %R% lookahead("-APPLE")
str_extract(test_string, rx)

Upvotes: 1

Joe
Joe

Reputation: 31087

See Regex group capture in R with multiple capture-groups for an example of using str_match(), from the stringr package.

In your case:

> test_string = c("ABC 2-APPLE", "123 25-APPLE", "DEF GHI 567-APPLE")
> 
> library(stringr)
> x <- str_match(test_string, " ([0-9]+)-APPLE$")[,2]
> as.numeric(x)
[1]   2  25 567

Upvotes: 1

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