# nth

##### Extract the first, last or nth value from a vector

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.

##### Usage

`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

- n
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.

- order_by
An optional vector used to determine the order

- default
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

```
# NOT RUN {
x <- 1:10
y <- 10:1
first(x)
last(y)
nth(x, 1)
nth(x, 5)
nth(x, -2)
nth(x, 11)
last(x)
# Second argument provides optional ordering
last(x, y)
# These functions always return a single value
first(integer())
# }
```

*Documentation reproduced from package dplyr, version 0.7.3, License: MIT + file LICENSE*