Strings need to have NAs set, lowercase and be trimmed before they can be checked. To avoid doing this multiple times, you can pass these processed values to the function.
nastrings
Vector of characters to be considered NAs. todate will treat these like NAs. Defaults to the easyr::nastrings list.
ifna
Action to take if NAs are created. 'return-unchanged' returns the sent vector unchanged; 'warning' results in a warning and returns the converted vector with new NAs; 'error' results in an error.