Just to help someone who's just voluntarily removed their question, following a request for code he tried and other comments. Let's assume they tried something like this:
str <- "How do I best try and try and try and find a way to to improve this code?"
d <- unlist(strsplit(str, split=" "))
paste(d[-which(duplicated(d))], collapse = ' ')
and wanted to learn a better way. So what is the best way to remove a duplicate word from the string?