Generating a repeating sequence an increasingly truncated number of times in R

Question

Consider some vector in R: x

x<-1:10

I'd like to create a repeating sequence of x , with the first element of each sequence truncated with each repetition, yielding the same output as would be given by issuing the following command in R:

c(1:10,2:10,3:10,4:10,5:10,6:10,7:10,8:10,9:10,10:10)

Can this be done? In reality, I'm working with a much larger vector for x . I'm playing with numerous combinations of the rep() function, to no avail.

Answer 1

Here's an alternative using mapply :

unlist(mapply(":", 1:10, 10))
#  [1]  1  2  3  4  5  6  7  8  9 10  2  3  4  5  6  7  8  9 10  3  4  5  6  7
# [25]  8  9 10  4  5  6  7  8  9 10  5  6  7  8  9 10  6  7  8  9 10  7  8  9
# [49] 10  8  9 10  9 10 10

Answer 2

A bit of a hack, because you can decompose what you are trying to do into two sequences:

rep(0:9, 10:1) + sequence(10:1)

You can see what each part does. I don't know if there is a way to feed the parameters to rep() or seq() like you would do in a Python expansion.

Answer 3

unlist(sapply(1:10, function(x) { x:10 }))