R Tutorial

Lists in R

A list in R is a data structure that can hold elements of different types — such as numbers, strings, vectors, and even other lists. This makes lists one of the most flexible data structures in R.

Creating a List

Use the list() function:

my_list <- list(
  name = "John",
  age = 25,
  scores = c(85, 90, 95),
  passed = TRUE
)
  

This list contains a string, a number, a numeric vector, and a logical value — all together.

Accessing List Elements

• my_list$name → Access by name
• my_list[["scores"]] → Access by name (alternative)
• my_list[[2]] → Access by index (2nd element)
• my_list[3] → Returns a sub-list (not the element directly)

Modifying List Elements

my_list$age <- 26       # Update age
my_list$city <- "Delhi" # Add new element
my_list$scores <- NULL  # Remove scores
  

Nested Lists

Lists can also contain other lists:

nested_list <- list(
  id = 101,
  info = list(
    name = "Alice",
    grade = "A"
  )
)
nested_list$info$name   # Access nested element
  

Useful List Functions

• length(list) – number of elements
• names(list) – shows names of elements
• str(list) – structure of the list
• unlist(list) – flattens the list into a vector

Summary

• Lists can hold different data types.
• Use list() to create them.
• Access with $, [[ ]], or [ ].
• Modify by assignment or remove using NULL.
• Lists can be nested inside other lists.

Practice Exercises

• Create a list with your name, age, and a vector of your top 3 skills.
• Access and print each element using both name and index methods.
• Add a new element to your list (like your city).
• Create a list that contains another list (nested).