How to match a substring at the end of a string in R?

Question

I'm using grepl to detect if a string includes a substring. For example:

grepl("-B4","P6-B4")

which obviously returns True. Now I want to avoid cases which have characters after the "-B4" substring. For example I want to see False from the following:

grepl("-B4","P6-B41A")

As you can see the reason I want to avoid it is because 4 is different from 41 and I don't want to detect 41. Thanks

Answer 1

grepl("-B4$",c("P6-B41A", "P6-B4"))
#[1] FALSE  TRUE

Answer 2

This seems like the perfect time to use endsWith() . It determines if a string ends with a specific character or series of characters.

endsWith(c("P6-B41A", "P6-B4"), "-B4")
# [1] FALSE  TRUE

And according to help(endsWith) , it's also more efficient than grepl() .

Answer 3

Another option would be to extract the last 3 characters and do a ==

substr(v1, nchar(v1)-2, nchar(v1)) == "-B4"
#[1] FALSE  TRUE

data

v1 <- c("P6-B41A", "P6-B4")