Most efficient way to select ending item of an array?

Question

I'm looking for the most efficent way (i.e. the lesser keys pressed) to indexing the last element of an array.

Then something like

a <- c(1,2,3)
n <- length(a)
b <- a[n]

should not be used, I would like to use just a single command.

In the example above I could use

b <- a[length(a)]

but I wonder if something shorter does exist.

Let I want to select a part of an array, like

a <- seq(from = 1, to = 10, by = 1)
b <- a[3:length(a)]

Is there a shorter way to do it?

Answer 1

For the first case, you can use:

> tail(a, 1)
[1] 3

Not that that really qualifies as shorter.

For the second example

> tail(a, -2)
[1]  3  4  5  6  7  8  9 10

but in general; no there is nothing shorter. R doesn't have an inplace operator or syntactic sugar for the end of a vector or array, in the sense of something that evaluates to the end of the array. That is what length() can be used for.