How can I change a full text to lowercase but retain the acronyms in uppercase using R? I need it for text mining and using udpi package. I could ofcourse use uppercase, but anyway to retain the uppercase acronyms while using lowercase?
tolower('NASA IS A US COMPANY').
tolower('NASA IS A US COMPANY')
tolower('NASA IS A US COMPANY')
Expected: NASA is a US company
Actual: nasa is a us company