Functions are useful when you want to perform a certain task multiple times. A function accepts input arguments and produces the output by executing valid commands that are inside the function. In R Programming Language when you are creating a function the function name and the file in which you are creating the function need not be the same and you can have one or more function definitions in a single R file. Types of function in R Language

Built-in Function Built function R is sq(), mean(), max(), these function are directly call in the program by users.

User-defile Function R language allow us to write our own function.

Functions in R programming are a way to encapsulate a set of instructions or operations into a reusable block of code. Functions allow programmers to organize code, improve code readability, and facilitate code reuse.

In R programming, functions are created using the function() keyword, followed by the function name, parameters (if any), and the body of the function enclosed in braces. Functions can take one or more input parameters and can return a value or a set of values.

For example, let's create a function in R that takes two input parameters a and b and returns their sum: 

sum_numbers <- function(a, b) {
  sum <- a + b
  return(sum)
}

Once the function is defined, it can be called multiple times with different input values: 

> sum_numbers(2, 3)
[1] 5
> sum_numbers(5, 7)
[1] 12

Functions in R can also be nested, which means that a function can be defined inside another function. This can be useful for creating more complex functions or for creating helper functions that are only used within the main function.

In conclusion, functions are an essential concept in R programming, and they provide a flexible way to encapsulate code and make it more organized, readable, and reusable.