# R Programming : Find the Factorial of a Number

Tutorial by:Maria Ghoste      Date: 2016-06-10 02:38:30

The factorial of a number is the product of all the integers from 1 to that number. For example, the factorial of 6 (denoted as 6!) is 1*2*3*4*5*6 = 720. Factorial is not defined for negative numbers and the factorial of zero is one, 0! = 1.

## Source Code

``````
# Program to find the
# factorial of a number
# provided by the user

# take input from the user
num = as.integer(readline(prompt="Enter a number: "))
factorial = 1

# check is the number is negative, positive or zero
if(num < 0) {
print("Sorry, factorial does not exist for negative numbers")
} else if(num == 0) {
print("The factorial of 0 is 1")
} else {
for(i in 1:num) {
factorial = factorial*i
}
print(paste("The factorial of",num,"is",factorial))
}``````

Output

```
Enter a number: 8
[1] "The factorial of 8 is 40320"
```

Here, we take input from the user and check if the number is negative, zero or positive using `if...else` statement. If the number is positive, we use `for` loop to calculate the factorial. We can also use the built-in function `factorial()` for this.

``````> factorial(8)
[1] 40320``````

## R Programming

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