Capitalize first word in a multiword string in R

Question

In R, how to capitalize only the first word in each string in a vector of single and multi-worded strings? The solutions I found (stringr::str_to_sentence(), stringr::str_to_title(), capitalize every word in the string.

Thanks!

strings <- c('one', 'one two', 'three four', 'five six')
expected.result <- c('One', 'One two', 'Three four', 'Five six')

Answer 1

strings <- c("one", "one two", "three four five", "six seven")

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stringr::str_to_sentence(strings)
[1] "One"             "One two"         "Three four five" "Six seven"      

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Base R:

sub("(\\w)", "\\U\\1", strings, perl = TRUE)
[1] "One"             "One two"         "Three four five" "Six seven"