data.table:last fails on date vectors

Question

last does not work on vectors of dates:

library(data.table)
f <- c("2014-11-10","2014-11-11")
last(f)
[1] "2014-11-11"
last(as.Date(f))
Error in last(as.Date(f)) : 
  data.table::last is trying to defer to xts::last because either x is not a vector, list, data.frame or data.table, or parameters such as 'n' or 'keep' have been provided as well. But xts hasn't been loaded.

the "helpful" message promised by ?last says that the argument is not a vector (it is!) and requires a package xts which I don't know about.

what is going on?

Answer 1

Pasting from comments above, is.vector(as.Date(f)) is FALSE , so it is not a vector. You need to first load xts using library(xts) and then load data.table and your code should work (since then data.table will be able to call xts::last on the Date object).