The **`factorial()` function** in `R` returns the factorial of a positive integer.

> A **factorial** is a product of that positive integer and all the integers below it until 1.

Figure 1 below shows the mathematical representation of the `factorial()` function and its corresponding representation in `R`.

# 
#  Syntax

---
```r
factorial(integer)
```
---

# 
## Parameter

This function requires a *positive* integer whose factorial is to be calculated.

##
## Return value

`factorial()` returns the factorial of the positive integer sent as a parameter.

---
> In the case of a `negative value`, a `warning` message is displayed along with `NaN`.
---

# 
## Code

The following example shows how we can use the `factorial()` function in `R`.

#example
a <- factorial(6);
print(paste0("factorial(6): ", a))

b <- factorial(4);
print(paste0("factorial(4): ", b))

c <- factorial(0);
print(paste0("factorial(0): ", c))

How to calculate the factorial() of a value in R

The factorial() function in R calculates the factorial of a positive integer, returning NaN for negatives.