Question

How can I check whether an integer vector is “sequential”, i.e. that the difference between subsequent elements is exactly one. I feel like I am missing something like “is.sequential”

Here’s my own function:

is.sequential <- function(x){
    all(diff(x) == rep(1,length(x)-1))
}    

Answer 1

There’s no need for rep since 1 will be recicled:

Edited to allow 5:2 as true

is.sequential <- function(x){
  all(abs(diff(x)) == 1)
}  

To allow for diferent sequences

is.sequential <- function(x){
 all(diff(x) == diff(x)[1])
}