R Functions

Functions are a blocks of code that perform a specific task.
They help in modularizing the code, making it more readable, maintainable, and reusable.

Syntax
function_name <- function(arg1, arg2, ...) {
# Function body
# Code to perform the task
return(result)
}

1. function_name - Declare a function name.
2. arg1, arg2, ... - Input parameters (arguments) either 0 or more that the function expects.
3. return(result) - The output that the functions expects.

# Define a function
add_numbers <- function(a, b) {
  result <- a + b
  return(result)
}

# Use the function
sum_result <- add_numbers(3, 5)
print(sum_result)  # Output: 8

You can place even more arguments and can use the function any number of times

Returning Multiple Values

You can return multiple values in one function.

# Function returning multiple values
calculate_stats <- function(data) {
  mean_value <- mean(data)
  median_value <- median(data)
  return(list(mean = mean_value, median = median_value))
}

# Use the function
data <- c(1, 2, 3, 4, 5)
stats <- calculate_stats(data)
print(stats$mean)
print(stats$median)

Here we used multiple values with its respective variable in a list form and return the values.
We use dollar ($) sign after the function name to get the value of a variable we want.

Anonymous Functions (Lambda Functions)

you can declare a statement in one line without return value

# Anonymous function (lambda function)
square <- function(x) x^2
# is equivalent to
square_lambda <- function(x) { return(x^2) }

# Use the anonymous function
result1 <- square(4)
result2 <- square_lambda(4)

Nested Functions

You can declare a function within other function

# Outer function
outer_function <- function(a, b) {
  
  # Nested function
  inner_function <- function(x, y) {
    result <- x + y
    return(result)
  }
  
  # Using the nested function
  nested_result <- inner_function(a, b)
  
  # Returning the result
  return(nested_result)
}

# Using the outer function
final_result <- outer_function(3, 5)
print(final_result)  # Output: 8

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