Get a seq() in R with alternating steps

Question

The seq function in R would give me a sequence from x to y with a constant step m:

seq(x, y, m)
         


        

Answer 1

Here is an alternative that uses diffinv This method over allocates the values, so as a stopping rule, I get the elements that are less than or equal to the stopping value.

seqAlt <- function(start, stop, by1, by2) {
   out <- diffinv(rep(c(by1, by2), ceiling(stop / (by1 + by2))), xi=start)
   return(out[out <= stop])
}

seqAlt(1, 19, 2, 4)
[1]  1  3  7  9 13 15 19