Vectors

The vector is R's basic data type: even a single number is a vector of length 1. Arithmetic and comparisons work on every element at once, so many loops in other languages are one expression in R.

scores <- c(70, 95, 82, 60)
print(scores * 2)
print(scores[scores > 75])
print(mean(scores))
print(sort(scores, decreasing = TRUE)[1:2])
print(length(scores))
print(seq(1, 10, by = 3))
print(1:5 + 10)
print(which(scores == max(scores)))
print(scores[-1])
print(rep(c("a", "b"), times = 2))

[1] 140 190 164 120
[1] 95 82
[1] 76.75
[1] 95 82
[1] 4
[1]  1  4  7 10
[1] 11 12 13 14 15
[1] 2
[1] 95 82 60
[1] "a" "b" "a" "b"

• Indexes start at 1. x[-1] means “all but the first”, not the last element.
• x[x > 75] keeps the elements where the condition is TRUE.
• A vector holds one type: c(1, "a") turns the number into text.
• Combining vectors of different lengths recycles the shorter one, which is easy to miss.