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R - Functions

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A function is a set of statements organized together to perform a specific job. R has a large number of in-built functions and the user can create their own functions.

In R, a function is an object and so the R interpreter is able to pass command to the function, along with arguments that may be necessary for the function to accomplish the deportment.

The role in plough performs its job and returns control to the interpreter besides as any result which may exist stored in other objects.

Function Definition

An R part is created by using the keyword role. The basic syntax of an R office definition is every bit follows −

function_name <- function(arg_1, arg_2, ...) {    Function body  }        

Role Components

The different parts of a role are −

• Function Name − This is the bodily name of the function. Information technology is stored in R environment as an object with this proper name.

• Arguments − An statement is a placeholder. When a function is invoked, y'all pass a value to the statement. Arguments are optional; that is, a part may contain no arguments. Likewise arguments can have default values.

• Function Trunk − The function torso contains a collection of statements that defines what the function does.

• Return Value − The return value of a function is the concluding expression in the function body to exist evaluated.

R has many in-congenital functions which can be directly called in the program without defining them first. We tin as well create and use our ain functions referred as user defined functions.

Built-in Function

Simple examples of in-built functions are seq(), mean(), max(), sum(x) and paste(...) etc. They are straight called by user written programs. You tin can refer virtually widely used R functions.

# Create a sequence of numbers from 32 to 44. impress(seq(32,44))  # Find mean of numbers from 25 to 82. impress(mean(25:82))  # Find sum of numbers frm 41 to 68. impress(sum(41:68))        

When we execute the above lawmaking, information technology produces the following consequence −

[ane] 32 33 34 35 36 37 38 39 40 41 42 43 44 [ane] 53.5 [one] 1526        

User-divers Function

Nosotros can create user-defined functions in R. They are specific to what a user wants and once created they tin can be used like the built-in functions. Below is an instance of how a office is created and used.

# Create a function to impress squares of numbers in sequence. new.function <- office(a) {    for(i in i:a) {       b <- i^2       print(b)    } }        

Calling a Function

# Create a part to impress squares of numbers in sequence. new.office <- part(a) {    for(i in one:a) {       b <- i^2       print(b)    } }  # Call the function new.function supplying 6 as an argument. new.function(six)        

When we execute the above code, it produces the following consequence −

[1] 1 [i] 4 [1] nine [i] xvi [one] 25 [1] 36        

Calling a Function without an Argument

# Create a function without an statement. new.function <- function() {    for(i in 1:v) {       print(i^2)    } }	  # Telephone call the function without supplying an statement. new.function()        

When we execute the higher up lawmaking, information technology produces the following outcome −

[1] i [1] 4 [1] 9 [1] 16 [i] 25        

Calling a Part with Argument Values (by position and by proper name)

The arguments to a function telephone call can be supplied in the same sequence every bit divers in the part or they can be supplied in a different sequence but assigned to the names of the arguments.

# Create a function with arguments. new.function <- function(a,b,c) {    result <- a * b + c    impress(event) }  # Call the role by position of arguments. new.office(v,3,xi)  # Call the function by names of the arguments. new.office(a = 11, b = five, c = 3)        

When we execute the above lawmaking, it produces the following result −

[one] 26 [1] 58        

Calling a Office with Default Argument

We tin define the value of the arguments in the role definition and call the office without supplying whatsoever statement to get the default result. But we can too telephone call such functions by supplying new values of the statement and go non default result.

# Create a function with arguments. new.role <- function(a = iii, b = 6) {    consequence <- a * b    impress(upshot) }  # Call the function without giving whatever argument. new.part()  # Phone call the function with giving new values of the argument. new.function(9,5)        

When we execute the above code, it produces the following result −

[1] 18 [one] 45        

Lazy Evaluation of Function

Arguments to functions are evaluated lazily, which means so they are evaluated only when needed by the function trunk.

# Create a function with arguments. new.function <- office(a, b) {    print(a^ii)    print(a)    print(b) }  # Evaluate the function without supplying one of the arguments. new.function(half dozen)        

When we execute the above code, it produces the following effect −

[1] 36 [1] half dozen Fault in print(b) : argument "b" is missing, with no default        

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Source: https://www.tutorialspoint.com/r/r_functions.htm

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