Split string when a capital letter follows a lower cap letter in the middle of a word in R

Question

I have some problems with different strings being concatenated and which I would like to split again. I am dealing with things such as

name="o-n-Butylhydroxylamine1-MethylpropylhydroxylamineAmino-2-butanol"

which in this case should be split in "o-n-Butylhydroxylamine", "1-Methylpropylhydroxylamine" and "Amino-2-butanol"

Any thoughts how I could use strsplit and/or gsub regular expression to achieve this? The rule I would like to use is that I would like to split a word when either a number, a bracket ("(") or a capital letter follows a lower caps letter. Any thoughts how to do this?

Answer 1

You could use positive look-around assertions to find (and then split at) inter-character positions preceded by a lower case letter and succeeded by an upper case letter, a digit, or a (.

name <- "o-n-Butylhydroxylamine1-MethylpropylhydroxylamineAmino-2-butanol"
pat <- "(?<=[[:lower:]])(?=[[:upper:][:digit:](])"
strsplit(name, pat, perl=TRUE)
# [[1]]
# [1] "o-n-Butylhydroxylamine"      "1-Methylpropylhydroxylamine"
# [3] "Amino-2-butanol"

Answer 2

strsplit(name, "(?<=([a-z]))(?=[A-Z]|[0-9]|\\()", perl=TRUE)
# [[1]]
# [1] "o-n-Butylhydroxylamine"      "1-Methylpropylhydroxylamine" "Amino-2-butanol"

Remember that the return value is a list, so use [[1]] if appropriate.