Math and Number Utilities in R

fib <- function(n) if (n < 2) n else fib(n-1) + fib(n-2)
out <- sapply(0:9, fib)
print(out)

[1] 0 1 1 2 3 5 8 13 21 34

n <- 5
fact <- 1
for (i in 2:n) fact <- fact * i
print(fact)

[1] 120

n <- 5
for (i in 1:10) {
  cat(n, "x", i, "=", n * i, "\n")
}

5 x 1 = 5
5 x 2 = 10
5 x 3 = 15
5 x 4 = 20
5 x 5 = 25
5 x 6 = 30
5 x 7 = 35
5 x 8 = 40
5 x 9 = 45
5 x 10 = 50

isPrime <- function(n) {
  if (n < 2) return(FALSE)
  if (n %% 2 == 0) return(n == 2)
  for (i in 3:floor(sqrt(n))) {
    if (n %% i == 0) return(FALSE)
  }
  TRUE
}
print(isPrime(29))

[1] TRUE

isArmstrong <- function(n) {
  digits <- as.integer(strsplit(as.character(n), "")[[1]])
  sum(digits^3) == n
}
print(isArmstrong(153))

[1] TRUE

n <- 10
a <- 0; b <- 1
out <- integer(n)
for (i in 1:n) {
  out[i] <- a
  t <- a + b
  a <- b; b <- t
}
print(out)

[1] 0 1 1 2 3 5 8 13 21 34

isLeap <- function(y) {
  (y %% 4 == 0 & y %% 100 != 0) | (y %% 400 == 0)
}
print(isLeap(2000))

[1] TRUE

fact <- function(n) if (n <= 1) 1 else n * fact(n - 1)
print(fact(5))

[1] 120

gcd <- function(a, b) { while (b != 0) { t <- b; b <- a %% b; a <- t } a }
print(gcd(24, 36))

[1] 12

gcd <- function(a, b) { while (b != 0) { t <- b; b <- a %% b; a <- t } a }
lcm <- function(a, b) abs(a*b) / gcd(a, b)
print(lcm(12, 18))

[1] 36

a <- "Hello"
b <- "World"
print(paste0(a, " ", b))

[1] "Hello World"