How to extract string from sentence using regex in R?

Question

I want to extract strings from the sentence using regex in R. And I'm new to R and don't where to begin or how to do it?

string<-c(".\n                Written by\nJ-S-Golden            \n        
\n        \n         \n                Plot Summary\n    |\n        Plot 
Synopsis\n    \n        \n            Plot Keywords:\n wrongful 
imprisonment\n                        |\n escape from prison\n                        
|\n based on the works of stephen king\n                        |\n 
prison\n                        |\n voice over narration\n            | See 
All (296) »      \n        \n            Taglines:\nFear can hold you 
prisoner. Hope can set you free.        \n        \n")

I have the string and I want in output is:

Plot Keywords:
\n wrongful imprisonment\n
|\n escape from prison\n
|\n based on the works of stephen king\n                        
|\n prison\n                        
|\n voice over narration\n            
| See All (296) »      \n        \n

I don't know how to extract clean data from the string. Can someone please help me.

Answer 1

Here is solution using base R's sub function. This matches (and includes) the leading text Plot Keywords: . Then, it uses a tempered dot to match any character until, but not including, the first following label followed by a colon.

sub("(?s).*(Plot Keywords:(?:(?![^: ]+:).)*).*", "\\1", string, perl=TRUE)

[1] "Plot Keywords:\n wrongful \nimprisonment\n
                    |\n escape from prison\n
                    \n|\n based on the works of
     stephen king\n
                    |\n \nprison\n                        |\n voice over narration\n
        | See \nAll (296) »      \n        \n            "

In this particular case, a pure regex demo might be more helpful than a R demo, so here is a link to one:

Demo