R factorial() function - Calculate factorial
R language examplesThe R factorial() function is used to calculate the factorial of a positive integer.
Factorial refers to the product of all integers from 1 to n, denoted as n!. It is very common in permutations, combinations, and probability calculations.
The syntax of the factorial() function is as follows:
factorial(x)
Parameter description:
xInput a non-negative integer or an integer vector.
Examples
# Calculate the factorial of a single value
print(factorial(5)) # 5! = 120
print(factorial(0)) # 0! = 1 (by convention)
print(factorial(10)) # 10! = 3628800
# Calculate the factorial for each element in the vector
x <- c(0, 1, 2, 3, 4, 5)
print(factorial(x))
print(factorial(5)) # 5! = 120
print(factorial(0)) # 0! = 1 (by convention)
print(factorial(10)) # 10! = 3628800
# Calculate the factorial for each element in the vector
x <- c(0, 1, 2, 3, 4, 5)
print(factorial(x))
Executing the above code outputs the following:
[1] 120 [1] 1 [1] 3628800 [1] 1 1 2 6 24 120
factorial() is often used together with choose() when calculating permutations and combinations:
Examples
# Manually calculate the number of permutations P(5, 3) = 5*4*3
n <- 5; k <- 3
permutation <- factorial(n) / factorial(n - k)
print(paste("P(5,3) =", permutation))
# Manually calculate the number of combinations C(5, 3) = P(5,3) / 3!
combination <- permutation / factorial(k)
print(paste("C(5,3) =", combination))
# Compare with R built-in functions
print(choose(5, 3))
n <- 5; k <- 3
permutation <- factorial(n) / factorial(n - k)
print(paste("P(5,3) =", permutation))
# Manually calculate the number of combinations C(5, 3) = P(5,3) / 3!
combination <- permutation / factorial(k)
print(paste("C(5,3) =", combination))
# Compare with R built-in functions
print(choose(5, 3))
Executing the above code outputs the following:
[1] "P(5,3) = 60" [1] "C(5,3) = 10" [1] 10Other extensions