How to deal with grep failure returning integer(0) in R?

You can use either length or identical

R> if (length(grep("w", data)) == 0) print ("ok")
[1] "ok"

R> if (identical(grep("w", data), integer(0))) print ("ok")
[1] "ok"

You could also use grepl instead of grep

R> if (!any(grepl("w", data))) print('ok')
[1] "ok"

Instead of grep, youcould use grepl which returns a logical:

> if (grepl("w",data)== FALSE) print ("ok") else print("donkeykong")
[1] "ok"


> if (grepl("h",data)== FALSE) print ("ok") else print("donkeykong")
[1] "donkeykong"