Given a vector, convert it to missing (NA) values,
where the class of the missing matches the input class.
Currently supports character, logical, integer, factor, numeric,
times (from chron), Date, POSIXct, POSIXlt, and
zoo (from zoo), and haven labelled from haven.
Usage
as.na(x)
Value
a vector the same length as the input with missing values of the same class