Create a list of vectors representing integers between the nth values of two equal length vectors in R

Question

I want to produce a list of unequal vectors, that represent the integers between the n th values of two existing vectors, n and L.

Example

 > n 
[1]   1   2   3   4   5   6   7

> L
[1]   2   2   4   4   4   4   4

For each value of n, I want to concatenate the integers between L and n when n>L, or retrieve the single value of n when L=n, or replace with value of 0 when L>n. I want to get a list (or other entity) with unequal vectors. Ideal output:

i
1 0
2 2
3 0
4 4
5 4 5
6 4 5 6
7 4 5 6 7

I have tried to use the colon operator (with the intention of replacing negative values later), eg

c((L):n) 

But it comes with the error:

numerical expression has 205 elements: only the first used

Answer 1

We can use Map

f1 <- function(x,y) c(x, if(x < y) 0 else if(x == y) x else y:x)
Map(f1, n, L)
#[[1]]
#[1] 1 0

#[[2]]
#[1] 2 2

#[[3]]
#[1] 3 0

#[[4]]
#[1] 4 4

#[[5]]
#[1] 5 4 5

#[[6]]
#[1] 6 4 5 6

#[[7]]
#[1] 7 4 5 6 7

If we need a vector

sapply(Map(f1, n, L), paste, collapse=" ")
#[1] "1 0"       "2 2"       "3 0"       "4 4"       "5 4 5"     "6 4 5 6"   "7 4 5 6 7"

---

Or if we just want to print it

for(i in seq_along(n))
 cat(c(n[i], if(n[i] < L[i]) 0 else if(n[i] == L[i]) n[i] else L[i]:n[i]), "\n")
#1 0 
#2 2 
#3 0 
#4 4 
#5 4 5 
#6 4 5 6 
#7 4 5 6 7 

Answer 2

A method using Reduce with accumulate = TRUE argument, giving a vector as a result

v1 <- ifelse(L > n, 0, ifelse(n == L, L, -1))
v1[v1 == -1] <- unique(unlist(Reduce(paste, x[v1==-1], y[v1==-1], accumulate = TRUE)))[-1]
#[1] "0"       "2"       "0"       "4"       "4 5"     "4 5 6"   "4 5 6 7"