Starting with incomplete cycle in rep()

Question

I want to generate a sequence where in a first step a random start number is chosen. Depending on the random start number (let's say: start_number = 3) I want to generate the following sequence. How can I do this?

seq_length <- 4
start_number <- sample(1:seq_length, 1, replace = TRUE) 

# Desired sequence
    int [1:100] 3 3 4 4 1 1 2 2 3 3 4 4 1 1 2 2 3 3 4 4 ...

Answer 1

You can use the repetition function:

rep(c(3,4,1,2), each = 2, length = 100)

num [1:100] 3 3 4 4 1 1 2 2 3 3 ...

if you want integers:

rep(c(3L,4L,1L,2L), each = 2, length = 100)

int [1:100] 3 3 4 4 1 1 2 2 3 3 ...

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Edit:

Since you said your start is random, here is a code to do this:

seq_length <- 4
start_number <- sample(seq_length, 1) 
b <- start_number:seq_length
rep(c(b, setdiff(1:seq_length, b)), each = 2, length=100)

[1] 2 2 3 3 4 4 1 1 2 2 3 3 4 4 1 1 2 2 3 3 4 4 ....