searching for the c++ in a string (regular expression) I want to find if a string contains c++ in it (regular expression). what pattern should I use in grep function in R? This is my error: Error in grep(pattern = "c++", x = df[trow, "modeling"]) : invalid regular expression 'c++', reason 'Invalid use of repetition operators'

If you want to grep for fixed strings use `fgrep` or `grep -F` instead. If you want to use `grep` the meta-characters like `+` needs to be escaped; there are various possibilities for that, e.g. `c[+][+]`.