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for loops in R have a reputation for being slow. The apply family is the idiomatic way to repeat operations:

sapply(x, f) — apply f to each element of x, simplify to a vector:

sapply(1:5, function(n) n * 2)   # 2 4 6 8 10
sapply(c("hi", "hello"), nchar)   # 2 5

lapply(x, f) — same but always returns a list (no simplification):

lapply(1:3, function(n) rep(n, n))
# list(1, c(2,2), c(3,3,3))

vapply(x, f, FUN.VALUE) — like sapply but with a guaranteed return type. Safer for production code.

Map(f, x, y) — multi-arg version. Map("+", 1:3, 10:12) → list(11, 13, 15).

These feel functional because they are. R draws heavily from Lisp's roots.