Remove strings that contain two or more capital letters from a vector in r

Question

I have the following vector for an example.

isotopes <- c("6Li", "7Li", "7LiH", "10B", "11B", "11BH")

I want to remove the strings "7LiH" and "11BH" from the vector. These values have two capital letters and so I am trying to figure out how to use grep to remove those values or just index out the other strings in the vector. How can I do this?

Answer 1

You can simply grep for elements that contain 2 or more capital letters and invert the match:

grep('[A-Z].*[A-Z]', isotopes, value=TRUE, invert=TRUE)

The regex matches a string that contains an uppercase letter, then probably something else and then one more uppercase letter (not necessary at the beginning or end)