Here's a possible stringi solution

library(stringi)
x &lt;- c("P1F2I235R15C145","P24F1I12R124C96")
res &lt;- stri_split_regex(x,"(?=([A-Za-z]=?))",perl = TRUE,simplify = TRUE,omit_empty = TRUE)
cbind.data.frame(x, res)
#                 x   1  2    3    4    5
# 1 P1F2I235R15C145  P1 F2 I235  R15 C145
# 2 P24F1I12R124C96 P24 F1  I12 R124  C96


How to split a string between two character into sub groups in R
So the description for protected tweets are: 


  Only confirmed followers have access to @foo's Tweets and complete profile. Click the "Follow" button to send a follow request.


But what if I tweet to a user who doesn't follow me, will he/she be able to see my tweet?

Hey, @userwhodoesnotfollowme can you see this tweet?

