R Sequences
A sequence is a vector whose values follow a steady pattern. R builds sequences with the colon operator and with the seq and rep functions.
Counting up and down
The colon operator counts up from 1 to 5. The second print counts back down from 5 to 1.
print(1:5)
print(5:1)Stepping with seq
seq starts at 1 and steps by 2. The steps stop at 9.
print(seq(1, 10, by = 2))A set count of steps
seq spreads five values from 0 to 1. The values land evenly between the two ends.
print(seq(0, 1, length.out = 5))Repeating a vector
rep makes a longer vector from the pair 1 and 2. The first print repeats the whole pair and the second repeats each value.
print(rep(c(1, 2), times = 2))
print(rep(c(1, 2), each = 2))Example
evens <- seq(2, 12, by = 2)
print(evens)
print(length(evens))
print(evens[4])Key points
- The colon operator counts up by one from the first value to the last.
- A colon range can also count down by one.
- seq builds a range with a chosen step size.
- The by argument of seq sets the size of each step.
- The length.out argument of seq sets how many values the result holds.
- rep repeats a vector to make a longer one.
- The times argument repeats the whole vector as one block.
- The each argument repeats each value before moving on.
In this example, seq builds the even numbers from 2 to 12. The length call counts six values. Index 4 then picks the fourth value.
Try it Yourself
Edit the code, then press Run.
Running is simulated · rdrr.io R Snippets
Exercise
What does rep(c(1, 2), each = 2) print?