R Functions
A function is a block of code which only runs when it is called.
You can pass data, known as parameters, into a function.
A function can return data as a result.
Creating a Function
To create a function, use the function() keyword:
Example
my_function <- function() { # create a function with the name my_function
print("Hello World!")
}
Call a Function
To call a function, use the function name followed by parenthesis, like my_function():
Example
my_function <- function() {
print("Hello World!")
}
my_function() # call the function named my_function
Try it Yourself »
Arguments
Information can be passed into functions as arguments.
Arguments are specified after the function name, inside the parentheses. You can add as many arguments as you want, just separate them with a comma.
The following example has a function with one argument (fname). When the function is called, we pass along a first name, which is used inside the function to print the full name:
Example
my_function <- function(fname) {
paste(fname, "Griffin")
}
my_function("Peter")
my_function("Lois")
my_function("Stewie")
Try it Yourself »
Parameters or Arguments?
The terms "parameter" and "argument" can be used for the same thing: information that are passed into a function.
From a function's perspective:
A parameter is the variable listed inside the parentheses in the function definition.
An argument is the value that is sent to the function when it is called.
Number of Arguments
By default, a function must be called with the correct number of arguments. Meaning that if your function expects 2 arguments, you have to call the function with 2 arguments, not more, and not less:
Example
This function expects 2 arguments, and gets 2 arguments:
my_function <- function(fname, lname) {
paste(fname, lname)
}
my_function("Peter", "Griffin")
Try it Yourself »
If you try to call the function with 1 or 3 arguments, you will get an error:
Example
This function expects 2 arguments, and gets 1 argument:
my_function <- function(fname, lname) {
paste(fname, lname)
}
my_function("Peter")
Try it Yourself »
Default Parameter Value
The following example shows how to use a default parameter value.
If we call the function without an argument, it uses the default value:
Example
my_function <- function(country = "Norway") {
paste("I am
from", country)
}
my_function("Sweden")
my_function("India")
my_function()
# will get the default value, which is Norway
my_function("USA")
Try it Yourself »
Return Values
To let a function return a result, use the return() function:
Example
my_function <- function(x) {
return (5 * x)
}
print(my_function(3))
print(my_function(5))
print(my_function(9))
Try it Yourself »
The output of the code above will be:
[1] 15
[1] 25
[1] 45
