R-带有特定排除项的grepl

Question

I was wondering how I can insert a specific exclusion pattern in a grepl .

Let us imagine, I want to seach for WHAM .

vec = c("WHAM VIDEO", "WHAM RAP", "WHAM", "HOTELNEWHAMP")
vec[grepl("WHAM", vec )]

What I get is

[1] "WHAM VIDEO"   "WHAM RAP"     "WHAM"         "HOTELNEWHAMP"

I can see that HOTELNEWHAMP is foreign.

How can I then vec[grepl("WHAM", vec )] and indicate clearly I do not want HOTELNEWHAMP ?

(not this vec[!grepl("HOTELNEWHAMP", vec )] because of course my real vector include many more variables).

Thanks

Answer 1

Use word boundaries.

vec = c("WHAM VIDEO", "WHAM RAP", "WHAM", "HOTELNEWHAMP")
vec[grepl("\\bWHAM\\b", vec )]
# [1] "WHAM VIDEO" "WHAM RAP"   "WHAM" 

or

vec[grepl("(?<!\\S)WHAM(?!\\S)", vec, perl=TRUE )]
# [1] "WHAM VIDEO" "WHAM RAP"   "WHAM"