In R does the fromLast argument in duplicated() work on integer64 vectors?

Question

I'm trying to identify duplicates in an integer64 vector using the fromLast argument in the duplicated() function (my rows are ordered in time and I want to discard the earlier time points, keeping the most recent unique value). It doesn't seem to work.

It works for regular integer vectors:

> x <- c(1, 2, 3, 3, 4)

> base::duplicated(x)
[1] FALSE FALSE FALSE  TRUE FALSE

> base::duplicated(x, fromLast = TRUE)
[1] FALSE FALSE  TRUE FALSE FALSE

This is the correct behavior.

But it doesn't work on an integer64 vector:

> x <- as.integer64(c(1, 2, 3, 3, 4))

> base::duplicated(x)
[1] FALSE FALSE FALSE  TRUE FALSE

> base::duplicated(x, fromLast = TRUE)
[1] FALSE FALSE FALSE  TRUE FALSE

Any ideas?

The duplicated.integer64() function doesn't have a fromLast argument.

I can do rev(duplicated(rev(x))) , but according to base R's documentation this is slower than using fromLast=TRUE .

Answer 1

The problem is in the method dispatched. It is calling the duplicated.integer64 . If we want the same behaviour, use duplicated.default

duplicated.default(x, fromLast = TRUE)
#[1] FALSE FALSE  TRUE FALSE FALSE

By checking the duplicated.integer64 , it doesn't have the fromLast argument

> duplicated.integer64
function (x, incomparables = FALSE, nunique = NULL, method = NULL, 
...) 

where as there is an argument for fromLast in duplicated.default

> duplicated.default
 function (x, incomparables = FALSE, fromLast = FALSE, nmax = NA, 
  ...) 

data

library(bit64)
x <- as.integer64(c(1, 2, 3, 3, 4))