Exclude elements from vector based on regular expression pattern

Question

I have some data which I want to clean up using a regular expression in R.

It is easy to find how to get elements that contain certain patterns, or do not contain certain words (strings), but I can't find out how to do this for excluding cells containing a pattern.

How could I use a general function to only keep those elements from a vector which do not contain PATTERN?

I prefer not to give an example, as this might lead people to answer using other (though usually nice) ways than the intended one: excluding based on a regular expression. Here goes anyway:

How to exclude all the elements that contain any of the following characters: 'pyfgcrl

vector <- c("Cecilia", "Cecily", "Cecily's", "Cedric", "Cedric's", "Celebes", 
            "Celebes's", "Celeste", "Celeste's", "Celia", "Celia's", "Celina")

The result would be an empty vector in this case.

Answer 1

Edit: From the comments, and with a little testing, one would find that my suggestion wasn't correct.

Here are two correct solutions:

vector[!grepl("['pyfgcrl]", vector)]                    ## kohske
grep("['pyfgcrl]", vector, value = TRUE, invert = TRUE) ## flodel

If either of them wants to re-post and accept credit for their answer, I'm more than happy to delete mine here.

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Explanation

The general function that you are looking for is grepl. From the help file for grepl:

grepl returns a logical vector (match or not for each element of x).

Additionally, you should read the help page for regex which describes what character classes are. In this case, you create a character class ['pyfgcrl], which says to look for any character in the square brackets. You can then negate this with !.

So, up to this point, we have something that looks like:

!grepl("['pyfgcrl]", vector)

To get what you are looking for, you subset as usual.

vector[!grepl("['pyfgcrl]", vector)]

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For the second solution, offered by @flodel, grep by default returns the position where a match is made, and the value = TRUE argument lets you return the actual string value instead. invert = TRUE means to return the values that were not matched.