Add space between two letters in a string in R [duplicate]

Question

Suppose I have a string like

s = "PleaseAddSpacesBetweenTheseWords"

How do I use gsub in R add a space between the words so that I get

"Please Add Spaces Between These Words"

I should do something like

gsub("[a-z][A-Z]", ???, s)

What do I put for ???. Also, I find the regular expression documentation for R confusing so a reference or writeup on regular expressions in R would be much appreciated.

Answer 1

You just need to capture the matches then use the \1 syntax to refer to the captured matches. For example

s = "PleaseAddSpacesBetweenTheseWords"
gsub("([a-z])([A-Z])", "\\1 \\2", s)
# [1] "Please Add Spaces Between These Words"

Of course, this just puts a space between each lower-case/upper-case letter pairings. It doesn't know what a real "word" is.