regex - Lower Case Certain Words R

Question

I need to convert certain words to lower case. I am working with a list of movie titles, where prepositions and articles are normally lower case if they are not the first word in the title. If I have the vector:

movies = c('The Kings Of Summer', 'The Words', 'Out Of The Furnace', 'Me And Earl And The Dying Girl')

What I need is this:

movies_updated = c('The Kings of Summer', 'The Words', 'Out of the Furnace', 'Me and Earl and the Dying Girl')

Is there an elegant way to do this without using a long series of gsub(), as in:

movies_updated = gsub(' In ', ' in ', movies)
movies_updated = gsub(' In', ' in', movies_updated)
movies_updated = gsub(' Of ', ' of ', movies)
movies_updated = gsub(' Of', ' of', movies_updated)
movies_updated = gsub(' The ', ' the ', movies)
movies_updated = gsub(' the', ' the', movies_updated)

And so on.

Answer 1

In effect, it appears that you are interested in converting your text to title case. This can be easily achieved with use of the stringi package, as shown below:

>> stringi::stri_trans_totitle(c('The Kings of Summer', 'The Words', 'Out of the Furnace'))
[1] "The Kings Of Summer" "The Words"           "Out Of The Furnace"

Alternative approach would involve making use of the toTitleCase function available in the the tools package:

>> tools::toTitleCase(c('The Kings of Summer', 'The Words', 'Out of the Furnace'))
[1] "The Kings of Summer" "The Words"           "Out of the Furnace"