R：传播向量的有效方法

Question

Is there an efficient way of programming to solve the following task?

Imagine the following vector:

A<-[a,b,c...k]

And would like to spread it the following way: Let's start with eg n=2

B<-[a,a,b,b,c...,k,k]

And now n=4 or any number greater 1

C<-[a,a,a,a,b,...,k,k,k,k]

To solve it via loops seems kind of easy, but is there any function or vector based operation I missed/could use? A tidyverse solutions (for using it in a pipe) would be the best solution for me.

(It is hard to do research on this task as I am a newbie in R and don't the correct terms to search for. Any help would be helpful.)

Answer 1

Let

A <- letters[1:11]
A
[1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k"

If you use function rep with argument each , you get what you want:

rep(A, each=2)
 [1] "a" "a" "b" "b" "c" "c" "d" "d" "e" "e" "f" "f" "g" "g" "h" "h" "i" "i" "j"
[20] "j" "k" "k"

rep(A, each=3)
[1] "a" "a" "a" "b" "b" "b" "c" "c" "c" "d" "d" "d" "e" "e" "e" "f" "f" "f" "g"
[20] "g" "g" "h" "h" "h" "i" "i" "i" "j" "j" "j" "k" "k" "k"

Answer 2

An option is to use rep with argument times = 2 or 4 and then sort the result. Another option is to use mapply and then c operator.

 c(mapply(rep, 2 ,A)) # OR sort(rep(A, times = 2))
 #[1] "a" "a" "b" "b" "c" "c" "d" "d" "e" "e" "f" "f" "g" "g" "h" "h" "i" "i" "j" "j"
 #[21] "k" "k"

 c(mapply(rep,A, 4))  #OR sort(rep(A, times = 2))
 #[1] "a" "a" "a" "a" "b" "b" "b" "b" "c" "c" "c" "c" "d" "d" "d" "d" "e" "e" "e" "e"
 #[21] "f" "f" "f" "f" "g" "g" "g" "g" "h" "h" "h" "h" "i" "i" "i" "i" "j" "j" "j" "j"
 #[41] "k" "k" "k" "k"