These are straightforward wrappers around [[. The main advantage is that you can provide an optional secondary vector that defines the ordering, and provide a default value to use when the input is shorter than expected.

nth(x, n, order_by = NULL, default = default_missing(x))

first(x, order_by = NULL, default = default_missing(x))

last(x, order_by = NULL, default = default_missing(x))



A vector


For nth_value(), a single integer specifying the position. Negative integers index from the end (i.e. -1L will return the last value in the vector).

If a double is supplied, it will be silently truncated.


An optional vector used to determine the order


A default value to use if the position does not exist in the input. This is guessed by default for base vectors, where a missing value of the appropriate type is returned, and for lists, where a NULL is return.

For more complicated objects, you'll need to supply this value. Make sure it is the same type as x.


A single value. [[ is used to do the subsetting.


x <- 1:10 y <- 10:1 first(x)
#> [1] 1
#> [1] 1
nth(x, 1)
#> [1] 1
nth(x, 5)
#> [1] 5
nth(x, -2)
#> [1] 9
nth(x, 11)
#> [1] NA
#> [1] 10
# Second argument provides optional ordering last(x, y)
#> [1] 1
# These functions always return a single value first(integer())
#> [1] NA