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))

## Arguments

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.

## Value

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

## Examples

x <- 1:10
y <- 10:1

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