Case Insensitive Unique keeping original

The easiest way to remove duplicates with case insensitive unique(tolower(x)) but it makes original values to lowercase. And I want to keep values as it is as there are some short-forms like SQL.

x <- c("SAS", "Machine Learning", "machine learning", "SQL")

>Solution :

You can try the code below using duplicated

x[!duplicated(tolower(x))]