A character class is how RegEx understands which characters should be considered for a match or “anti-match”—anything but what is shown. Note that “class” in this context has nothing to do with the R statement “class(x),” which gives you the class of object x.
Character classes start out simple. Just enclose match characters in brackets. [fk] means select anything containing a “f” or “k.” It does not matter which one is first, and you can have as many letters, numbers, or anything else you need.
A hyphen between two characters indicates ...
