su: ignore --preserve-environment, it's mutually exclusive to --login.
Error in eval(quote({ : 
  You are attempting to load an rmarkdown file, but the 
rmarkdown package was not found in the library. Ensure that 
rmarkdown is installed and is available in the Library of the 
user you're running this application as.
Calls: local -> eval.parent -> eval -> eval -> eval -> eval
Execution halted