Functions are used to logically break our code into simpler parts which become easy to maintain and understand.
It's pretty straightforward to create your own function in R programming.
Syntax for R Functions
The syntax for writing R function is:
func_name <- function (argument) {
statement
}
Here, we can see that the reserved word function is used to declare a function in R.
- The statements within the curly braces form the body of the function. These braces are optional if the body contains only a single expression.
- Finally, this function object is given a name by assigning it to a variable,
func_name
Example of a Function
pow <- function(x, y) {
# function to print x raised to the power y
result <- x^y
print(paste(x,"raised to the power", y, "is", result))
}
Here, we created a function called pow().
It takes two arguments, finds the first argument raised to the power of the second argument and prints the result in appropriate format.
We have used a built-in function paste() which is used to concatenate strings.
How to call a function?
Let's call the function pow() that we created above. We can call the above function as follows:
pow(8, 2)
pow(2, 8)
Output
[1] "8 raised to the power 2 is 64" [1] "2 raised to the power 8 is 256"
Here, the arguments used in the function declaration (x and y) are called formal arguments and those used while calling the function are called actual arguments.
Named Arguments
In the above function calls, the matching of formal arguments to the actual arguments takes place in positional order.
This means that, in the call pow(8,2), the formal arguments x and y are assigned 8 and 2 respectively.
We can also call the function using named arguments.
When calling a function in this way, the order of the actual arguments doesn't matter. For example, all of the function calls given below are equivalent.
pow(8, 2)
pow(x = 8, y = 2)
pow(y = 2, x = 8)
Output
[1] "8 raised to the power 2 is 64" [1] "8 raised to the power 2 is 64" [1] "8 raised to the power 2 is 64"
Furthermore, we can use named and unnamed arguments in a single call.
In such a case, all the named arguments are matched first and then the remaining unnamed arguments are matched in a positional order.
pow(x=8, 2)
pow(2, x=8)
Output
[1] "8 raised to the power 2 is 64" [1] "8 raised to the power 2 is 64"
In all the examples above, x gets the value 8 and y gets the value 2.
Default Values for Arguments
We can assign default values to arguments in a function in R.
This is done by providing an appropriate value to the formal argument in the function declaration.
Here is the above function with a default value for y.
pow <- function(x, y = 2) {
# function to print x raised to the power y
result <- x^y
print(paste(x,"raised to the power", y, "is", result))
}
The use of default value to an argument makes it optional when calling the function.
pow(3)
pow(3,1)
Output
[1] "3 raised to the power 2 is 9" [1] "3 raised to the power 1 is 3"
Here, y is optional and will take the value 2 when not provided.
Check out these examples to learn more: