Create sequence between certain values across two vectors

Question

I am currently trying to create sequences between values of different vectors that do not have the same length.

Imagine I have the two following vectors a and b:

a<-c(1, 8, 14, 34, 46, 55)
b<-c(3, 6, 12, 13, 18, 42, 49, 50, 57, 200)

I would like to generate a third vector that shows the sequences between the values of a and the next highest value of b (here: 1:3 as 1,2,3; 8:12 as 8,9,10,11,12; 14:18 as 14,15,16,17,18 and so on until finally 55:57 as 55,56,57).

Using mapply did not yield the desired results.

Answer 1

We can use findInterval to subset the 'b' based on the value of 'a' and then with Map get the corresponding sequence (:=) between the elements of the 'a' and the subset elements of 'b'

Map(`:`, a, b[findInterval(a, b) + 1])
#[[1]]
#[1] 1 2 3

#[[2]]
#[1]  8  9 10 11 12

#[[3]]
#[1] 14 15 16 17 18

#[[4]]
#[1] 34 35 36 37 38 39 40 41 42

#[[5]]
#[1] 46 47 48 49

#[[6]]
#[1] 55 56 57