R Language Basics I

Fundamentals of R programming covering introductory concepts to data frames
Author

David Munoz Tord

Published

March 12, 2025

Introduction to R

R is a powerful programming language for statistical computing and data analysis. Originally developed by statisticians Ross Ihaka and Robert Gentleman at the University of Auckland in the 1990s, R has become a leading tool for data science, statistical analysis, and data visualization.

Think of R as the Swiss Army knife of the data world – it may not look as flashy as some newer tools, but it’s powerful, reliable, and has a tool for every statistical job imaginable!

Key Features of R:

  • Statistical Focus: R was built specifically for statistical analysis and offers a vast array of statistical methods and tests. It’s like having a statistical superhero at your fingertips!
  • Graphics Capabilities: Excellent for creating high-quality visualizations with packages like ggplot2. Your data deserves a glow-up too!
  • Extensibility: Thousands of packages available through CRAN (Comprehensive R Archive Network) extend R’s functionality. It’s like the App Store for statistics nerds!
  • Open Source: Free and open-source, with a strong community of users and developers. In a world of expensive software, R is like Robin Hood – taking powerful statistical capabilities from the wealthy software giants and giving them to everyone.
  • Interactive Environment: The R console provides immediate feedback, making it ideal for data exploration. It’s like having a conversation with your data!

The R Console and Basic Operations

When you start R, you’re presented with a console where you can enter commands. The console interprets each command and returns results immediately.

R functions as a sophisticated calculator, capable of handling basic arithmetic operations and much more. Here are some basic operations you can perform:

# Addition: Like when Darth Vader and Luke Skywalker finally team up
5 + 3  # Returns 8

# Subtraction: Like when you realize how much Starbucks costs monthly
10 - 4  # Returns 6

# Multiplication: What happens to your problems when you tell your mom
6 * 7  # Returns 42 (also the answer to the ultimate question of life, the universe, and everything)

# Division: Sharing pizza with friends
20 / 5  # Returns 4

# Exponentiation (Power): Like when a superhero discovers their abilities
2^3  # Returns 8

Exercise 1: Basic R Operations

Perform the following operations in R: 1. Add 25 and 75 2. Multiply 10 by 5 3. Divide 100 by 4

_webr_editor_1 = Object {code: null, options: Object, indicator: it}
Hint

Use the standard arithmetic operators: + for addition, * for multiplication, and / for division. Even Jar Jar Binks could do this!

Solution: 
# Addition
25 + 75

# Multiplication
10 * 5

# Division
100 / 4

Comments and Output in R

R allows you to add comments to your code to explain what it does. Comments start with the # symbol and are ignored by R when executing code, like how everyone ignores the terms and conditions before clicking “I agree.”

R automatically prints the result of a calculation or command if it’s not assigned to a variable. This feature is useful for quick calculations and checking intermediate results.

You can also explicitly print values using the print() function, which is especially useful when working with scripts where automatic printing doesn’t occur.

# This is a comment that R ignores (like when your cat ignores you)

# Automatic printing example
42  # R will output 42, the answer to everything according to "The Hitchhiker's Guide to the Galaxy"

# Print function example
print("Help me Obi-Wan Kenobi, you're my only hope")  # Explicitly prints the message

Exercise 2: Printing and Comments

Practice printing values and adding comments to your code.

_webr_editor_2 = Object {code: null, options: Object, indicator: it}
Hint

Use # to add comments. R will automatically print the result of an expression if it’s not assigned to a variable. You can also use the print() function, which is like using a megaphone for your data.

Solution: 
# This is a comment - it's like whispering to your code

# Automatic printing
42  # The answer to life, the universe, and everything

# Print function
print("I find your lack of comments disturbing")

# Multiple operations
2 + 2  # This is the way
print(10 * 5)  # May the force be with you

Names and Assignment

In R, you can store values in variables for later use. This is done using the assignment operator, which can be either <- or =. The <- operator is more commonly used in R programming.

Variable Assignment

When you assign a value to a variable, R stores that value in memory. You can then use the variable name to refer to that value in subsequent operations. It’s like giving a name to your pet dragon so you can call it later.

# Assign value 10 to variable x
x <- 10

# Use x in a calculation
x + 5  # Returns 15

# Reassign x to a new value
x <- 20
x  # Now returns 20, because x had a change of heart

While both <- and = work for assignment in most contexts, <- is preferred in R programming because it clearly distinguishes assignment from the == equality test and because it works in all contexts. It’s like the difference between “your” and “you’re” - both sound the same, but using the wrong one can lead to confusion!

Variable Names

Good variable names are essential for readable code. In R:

  • Variable names can contain letters, numbers, dots (.), and underscores (_)
  • Names must start with a letter or a dot not followed by a number
  • Names are case-sensitive (jedi and Jedi are different variables)
  • Names should be descriptive of what they contain
# Valid variable names
age_of_yoda <- 900
harry.potter <- "The Boy Who Lived"
vader_rage_level <- 95

# Invalid variable names (would cause errors)
# 2fast2furious <- "Great movie"  # Can't start with a number
# iron-man <- "Tony Stark"      # Can't contain hyphens

Exercise 3: Variable Assignment

Create variables for the following: 1. Assign the value 42 to a variable named answer_to_everything 2. Assign the text “May the Force be with you” to a variable named jedi_greeting 3. Assign the result of 25 * 4 to a variable named lightsaber_power

_webr_editor_3 = Object {code: null, options: Object, indicator: it}
Hint

Use the assignment operator <- to assign values to variables. Even a young padawan can master this skill!

Solution: 
# Assign numeric value
answer_to_everything <- 42

# Assign text (character) value
jedi_greeting <- "May the Force be with you"

# Assign result of calculation
lightsaber_power <- 25 * 4

# Print the variables
answer_to_everything
jedi_greeting
lightsaber_power

Data Types in R

R has several basic data types:

  1. Numeric: Decimal numbers (1.5, 42.0) - like counting how many times Thanos snaps
  2. Integer: Whole numbers (1L, 42L, where the L indicates an integer) - like counting Stormtroopers
  3. Character: Text, enclosed in quotes ("hello", 'R is fun') - like famous movie quotes
  4. Logical: Boolean values (TRUE or FALSE) - like asking “Is Darth Vader Luke’s father?”
  5. Complex: Complex numbers with real and imaginary parts (1+2i) - like quantum physics that powers Iron Man’s suit
  6. Date: Date values (as.Date("2023-01-15")) - like keeping track of when the Death Star was destroyed

You can check the type of any variable using the class() function.

# Numeric
death_star_diameter <- 160.0
class(death_star_diameter)  # Returns "numeric"

# Integer
stormtrooper_count <- 10000L
class(stormtrooper_count)  # Returns "integer"

# Character
yoda_quote <- "Do or do not, there is no try"
class(yoda_quote)  # Returns "character"

# Logical
is_vader_lukes_father <- TRUE
class(is_vader_lukes_father)  # Returns "logical"

# Date
alderaan_destruction <- as.Date("1977-05-25")
class(alderaan_destruction)  # Returns "Date"

Exercise 4: Variable Types

Create variables of different types and check their class:

_webr_editor_4 = Object {code: null, options: Object, indicator: it}
Hint

Use the class() function to check the type of a variable. Create variables of different types and check their class. It’s like figuring out if someone is a Jedi, Sith, or just a regular human.

Solution: 
# Numeric variable
millennium_falcon_speed <- 1050
class(millennium_falcon_speed)

# Integer variable (note the L suffix)
rebel_fighters <- 30L
class(rebel_fighters)

# Character variable
vader_quote <- "I am your father"
class(vader_quote)

# Logical variable
han_shot_first <- TRUE
class(han_shot_first)

# Date variable
endgame_release <- as.Date("2019-04-26")
class(endgame_release)

Vectors

Vectors are one of the most basic and important data structures in R. A vector is a sequence of data elements of the same type. It’s like a collection of values stored together - think of it as your collection of Star Wars action figures, but all of the same type (all Jedi, all Sith, etc.).

Creating Vectors

There are several ways to create vectors in R:

  1. Using the c() function (combine function):

    # Create a numeric vector
jedi_power_levels <- c(80, 95, 75, 99, 60)

# Create a character vector
hogwarts_houses <- c("Gryffindor", "Hufflepuff", "Ravenclaw", "Slytherin")

  2. Using the colon operator : for sequences:

    # Create a sequence from 1 to 10
countdown_to_blastoff <- 10:1  # Contains 10, 9, 8, ..., 1

  3. Using the seq() function for more complex sequences:

    # Create a sequence from 0 to 1 with 0.1 steps
lightsaber_power_settings <- seq(0, 1, by = 0.1)  # 0, 0.1, 0.2, ..., 1

  4. Using the rep() function to repeat values:

    # Repeat "I am Groot" five times
groot_dialogue <- rep("I am Groot", times = 5)  # I am Groot, I am Groot, I am Groot...

Vector Types

All elements in a vector must be of the same type. The main vector types are:

  • Numeric vectors: contain numbers (c(3.14, 2.718, 1.618)) - like the scores in Olympic lightsaber throwing
  • Integer vectors: contain whole numbers (c(1L, 2L, 3L)) - like counting Infinity Stones
  • Character vectors: contain text (c("Luke", "Leia", "Han")) - like your favorite Star Wars characters
  • Logical vectors: contain TRUE or FALSE values (c(TRUE, FALSE, TRUE)) - like whether each Avenger survived “the snap”
  • Date vectors: contain date values - like important Star Wars movie release dates

Exercise 5: Creating Vectors

Create vectors using different methods:

_webr_editor_5 = Object {code: null, options: Object, indicator: it}
Hint

Use c() to combine values into a vector. Use : for a sequence of consecutive numbers. It’s not rocket science… well, maybe it is if you’re building vectors for the Death Star trajectory.

Solution: 
# Create a numeric vector using c()
jedi_council_power <- c(95, 88, 92, 99, 85)
jedi_council_power

# Create a sequence using :
order_66_victims <- 1:10
order_66_victims

# Create a character vector
rebel_alliance <- c("Luke", "Leia", "Han", "Chewie", "R2-D2")
rebel_alliance

# Create a logical vector
survived_death_star <- c(TRUE, TRUE, TRUE, FALSE, TRUE)
survived_death_star

Vector Operations

R is designed to work efficiently with vectors. Most operations are “vectorized,” meaning they apply to each element of the vector automatically. This is like having Force powers that affect multiple objects at once!

Arithmetic with Vectors

When you perform arithmetic operations on vectors, R applies the operation to each element:

# Vector addition
c(1, 2, 3) + c(4, 5, 6)  # Returns c(5, 7, 9)

# Vector multiplication - like calculating damage multipliers in a video game
c(1, 2, 3) * 2  # Returns c(2, 4, 6)

Vector Recycling

If vectors have different lengths, R “recycles” the shorter vector to match the length of the longer one:

# Vector of length 3 plus vector of length 1
# Like adding a power-up to each character in a game
c(1, 2, 3) + 10  # Returns c(11, 12, 13)

# Vector of length 3 plus vector of length 2
# Like trying to pair Jedi with lightsabers when you don't have enough lightsabers
c(1, 2, 3) + c(10, 20)  # Returns c(11, 22, 13), with warning

Vector Functions

R has many built-in functions for working with vectors:

x <- c(2, 4, 6, 8, 10)  # Midi-chlorian counts for different Jedi

length(x)    # Returns 5 (number of Jedi)
sum(x)       # Returns 30 (total midi-chlorian count)
mean(x)      # Returns 6 (average midi-chlorian count)
median(x)    # Returns 6 (median midi-chlorian count)
min(x)       # Returns 2 (lowest midi-chlorian count)
max(x)       # Returns 10 (highest midi-chlorian count)
sort(x)      # Returns sorted vector (arranging Jedi by power)
rev(x)       # Returns reversed vector (from most to least powerful)

Exercise 6: Vector Operations

Perform operations on vectors:

Exercise
Start Over Show Hint
Run Code
# Pre-defined vectors
jedi_power <- c(80, 85, 95, 75, 90)
sith_power <- c(85, 80, 90, 95, 85)
_webr_editor_6 = Object {code: null, options: Object, indicator: it}
Hint

You can perform arithmetic operations on vectors element-by-element. Use functions like length(), sum(), mean(), etc. to get information about vectors. It’s like comparing the power levels of Jedi and Sith!

Solution: 
# Pre-defined vectors
jedi_power <- c(80, 85, 95, 75, 90)
sith_power <- c(85, 80, 90, 95, 85)

# Vector addition - combined power
jedi_power + sith_power

# Vector multiplication - power amplification
jedi_power * 1.5

# Vector length - how many Jedi
length(jedi_power)

# Sum of vector elements - total Jedi power
sum(jedi_power)

# Mean of vector elements - average Sith power
mean(sith_power)

# Min and max - weakest and strongest Jedi
min(jedi_power)
max(jedi_power)

# Who is more powerful in each matchup?
jedi_power > sith_power

Operators

Operators are symbols that tell R to perform specific mathematical or logical operations. R has a rich set of operators that allow you to perform various calculations and comparisons.

Arithmetic Operators

Arithmetic operators perform mathematical calculations:

Operator Description Example Result
+ Addition 5 + 3 8 (like combining forces)
- Subtraction 5 - 3 2 (like losing health points)
* Multiplication 5 * 3 15 (like power-ups)
/ Division 5 / 3 1.666667 (like sharing loot)
^ Exponentiation 5 ^ 3 125 (like leveling up)
%% Modulus (remainder) 5 %% 3 2 (like leftover pizza slices)
%/% Integer Division 5 %/% 3 1 (like whole portions in Jakku)

These operators can work on single values or vectors, applying the operation to each element of the vector.

# Vector arithmetic
c(1, 2, 3) + c(4, 5, 6)  # Returns c(5, 7, 9)
c(1, 2, 3) * 2           # Returns c(2, 4, 6)

Exercise 7: Arithmetic Operators

Use various arithmetic operators in R:

_webr_editor_7 = Object {code: null, options: Object, indicator: it}
Hint

Common arithmetic operators in R include: + (addition), - (subtraction), * (multiplication), / (division), ^ (exponentiation), %% (modulo), %/% (integer division). Use the Force, young padawan!

Solution: 
# Addition (combining rebel forces)
10 + 5

# Subtraction (stormtroopers lost in battle)
10 - 5

# Multiplication (cloning troopers)
10 * 5

# Division (sharing rations)
10 / 3

# Exponentiation (power amplification)
2 ^ 3

# Modulo (remainder after dividing portions)
10 %% 3

# Integer division (whole portions only)
10 %/% 3

Comparison Operators

Comparison operators compare values and return logical (TRUE/FALSE) results:

Operator Description Example Result
== Equal to yoda_age == 900 TRUE
!= Not equal to yoda_species != "human" TRUE
< Less than luke_power < vader_power TRUE (initially)
> Greater than falcon_speed > tie_fighter_speed TRUE
<= Less than or equal to han_solo_coolness <= chewbacca_coolness FALSE
>= Greater than or equal to death_star_size >= alderaan_size TRUE (unfortunately)

These operators are essential for filtering data and controlling program flow with conditionals.

Logical Operators

Logical operators combine logical (TRUE/FALSE) values:

Operator Description Example Result
& Element-wise AND c(TRUE, FALSE) & c(TRUE, TRUE) c(TRUE, FALSE)
| Element-wise OR c(TRUE, FALSE) | c(FALSE, TRUE) c(TRUE, TRUE)
! NOT !TRUE FALSE
&& AND (single value) is_jedi && has_lightsaber Depends on values
|| OR (single value) is_jedi || is_sith Depends on values

The element-wise operators (&, |) work on vectors, while the single-value operators (&&, ||) only evaluate the first element of vectors.

# Element-wise AND
jedi_skills <- c(TRUE, FALSE, TRUE)
force_sensitive <- c(TRUE, TRUE, FALSE)
can_use_force <- jedi_skills & force_sensitive  # Returns c(TRUE, FALSE, FALSE)

# Single-value AND (uses only first element)
is_a_jedi <- jedi_skills && force_sensitive  # Returns TRUE

Exercise 8: Comparison Operators

Use comparison operators and logical operators:

Exercise
Start Over Show Hint
Run Code
vader_power <- 95
luke_power <- 85
_webr_editor_8 = Object {code: null, options: Object, indicator: it}
Hint

Comparison operators include: == (equal), != (not equal), > (greater than), < (less than), >= (greater than or equal), <= (less than or equal). Logical operators include: & (AND), | (OR), ! (NOT). Use them to compare the power levels of Vader and Luke!

Solution: 
vader_power <- 95
luke_power <- 85

# Comparison operators
vader_power == luke_power  # Are they equally powerful?
vader_power != luke_power  # Are they different in power?
vader_power > luke_power   # Is Vader more powerful?
luke_power < vader_power   # Is Luke less powerful?
vader_power >= 90  # Is Vader's power at least 90?
luke_power <= 80   # Is Luke's power at most 80?

# Logical operators
(vader_power > 90) & (luke_power > 80)  # Are both powerful?
(vader_power > 100) | (luke_power > 80)  # Is at least one very powerful?
!(vader_power == luke_power)  # Are they not equal in power?

Factors and Lists

Factors

Factors are a special type of vector used to represent categorical data. They are particularly useful in statistical modeling and data visualization. Think of them as sorting your Star Wars action figures by type: Jedi, Sith, droids, etc.

Creating Factors

Factors are created using the factor() function. By default, R will sort the levels alphabetically, but you can specify a custom order if needed.

# Create a basic factor
jedi_or_sith <- factor(c("Jedi", "Sith", "Sith", "Jedi", "Jedi"))
jedi_or_sith  # Levels: Jedi Sith

# Specify custom levels (including order)
force_alignment <- factor(c("Light", "Dark", "Grey", "Light", "Dark"), 
                     levels = c("Light", "Grey", "Dark"))
force_alignment  # Levels: Light Grey Dark

Working with Factors

Factors are useful for:

  1. Ensuring data consistency: Only values in the defined levels are allowed (no “Gungan” in your Jedi/Sith classification)
  2. Controlling the order of categories: Important for plots and tables (Light side always comes first!)
  3. Efficient storage: Factors store integers internally with a lookup table
  4. Statistical modeling: Proper handling of categorical variables

Common functions used with factors:

# Get the levels of a factor
levels(jedi_or_sith)  # Returns "Jedi" "Sith"

# Count occurrences of each level
table(jedi_or_sith)  # Shows frequency table - how many Jedi vs Sith

# Convert factor to numeric
as.numeric(force_alignment)  # Returns the underlying integer codes

# Convert factor to character
as.character(force_alignment)  # Returns the original strings

Exercise 9: Creating and Working with Factors

Create and manipulate factors:

_webr_editor_9 = Object {code: null, options: Object, indicator: it}
Hint

Factors are used to represent categorical data. Use the factor() function to create factors. You can specify the levels using the levels parameter. It’s like organizing your Marvel heroes by team affiliation!

Solution: 
# Create a vector of Star Wars species
species <- c("Human", "Wookiee", "Droid", "Human", "Twi'lek", "Droid", "Human")

# Convert to factor
species_factor <- factor(species)
species_factor

# Check levels
levels(species_factor)

# Create Hogwarts houses factor with specified levels
hogwarts_houses <- factor(c("Gryffindor", "Slytherin", "Hufflepuff", "Ravenclaw", "Gryffindor"), 
                 levels = c("Gryffindor", "Hufflepuff", "Ravenclaw", "Slytherin"))
hogwarts_houses

# Count occurrences
table(species_factor)
table(hogwarts_houses)

Lists

Lists are a versatile data structure in R that can hold elements of different types, including other lists. This makes them ideal for hierarchical or heterogeneous data. Think of a list as your utility belt - it can hold all sorts of gadgets (data types) at once!

Creating Lists

Lists are created using the list() function. Each element can have a name for easier access.

# Create a basic list
batmans_utility_belt <- list(100, "Batarang", TRUE, c(1, 2, 3))

# Create a named list
han_solo <- list(
  name = "Han Solo",
  age = 32,
  ships = c("Millennium Falcon", "Stolen Imperial Shuttle"),
  is_scoundrel = TRUE
)

Accessing List Elements

There are multiple ways to access elements in a list:

  1. Using double square brackets [[]] for a single element:

    han_solo[[1]]        # Returns "Han Solo"
han_solo[["name"]]   # Returns "Han Solo"

  2. Using the dollar sign $ for named elements:

    han_solo$name        # Returns "Han Solo"
han_solo$ships[1]    # Returns "Millennium Falcon"

  3. Using single square brackets [] to get a sublist:

    han_solo[1:2]        # Returns a list with name and age
han_solo["ships"]    # Returns a list with just the ships element

Modifying Lists

Lists are mutable, so you can change them after creation:

# Add a new element
han_solo$friends <- c("Luke", "Leia", "Chewie")

# Change an existing element
han_solo$age <- 35

# Remove an element
han_solo$is_scoundrel <- NULL  # Han's grown up a bit

Exercise 10: Working with Lists

Create and manipulate lists:

_webr_editor_10 = Object {code: null, options: Object, indicator: it}
Hint

Lists can contain elements of different types. Use the list() function to create lists. Access elements using [[]] or $ for named elements. Think of it as creating a character profile for your favorite superhero or villain!

Solution: 
# Create a list with different types
darth_vader <- list(
  name = "Anakin Skywalker",
  sith_name = "Darth Vader",
  age = 45,
  midi_chlorian_count = c(27000, 23000, 20000),  # decreasing over time
  is_lukes_father = TRUE
)

# Display the list
darth_vader

# Access elements
darth_vader[[1]]  # First element
darth_vader$sith_name  # Element by name
darth_vader$midi_chlorian_count[1]  # Element within element

# Add element to list
darth_vader$famous_line <- "I am your father"
darth_vader

Data Frames

Data frames are the most common data structure for tabular data in R. They’re similar to tables in a database, spreadsheets, or CSV files. Think of them as the Galactic Senate records - neatly organized information about various entities.

Key Features of Data Frames

  • Rectangular data (rows and columns)
  • Each column can be a different data type
  • All columns must have the same length
  • Each column has a name
  • Rows can be named (but often aren’t)

Creating Data Frames

Data frames are created using the data.frame() function:

# Create a data frame of Star Wars characters
star_wars_chars <- data.frame(
  name = c("Luke", "Leia", "Han", "Chewie"),
  species = c("Human", "Human", "Human", "Wookiee"),
  force_sensitive = c(TRUE, TRUE, FALSE, FALSE),
  age = c(19, 19, 29, 200)
)

You can also create data frames from external sources using functions like: - read.csv() - read from CSV files - read.table() - read from text files - read_excel() - read from Excel files (requires the readxl package)

Examining Data Frames

R provides several functions to examine data frames:

# View the structure of a data frame
str(star_wars_chars)

# Show the first few rows
head(star_wars_chars)

# Show the last few rows
tail(star_wars_chars)

# Get a summary of the data frame
summary(star_wars_chars)

# Get the dimensions (rows, columns)
dim(star_wars_chars)

# Get the column names
names(star_wars_chars)

Exercise 11: Creating Data Frames

Create a data frame to store structured data:

_webr_editor_11 = Object {code: null, options: Object, indicator: it}
Hint

A data frame is a table-like structure where each column can contain data of a different type. Use the data.frame() function to create data frames. It’s like creating your own superhero database!

Solution: 
# Create a data frame of Avengers
avengers <- data.frame(
  name = c("Iron Man", "Captain America", "Thor", "Hulk"),
  real_name = c("Tony Stark", "Steve Rogers", "Thor Odinson", "Bruce Banner"),
  age = c(40, 95, 1500, 42),
  is_original = c(TRUE, TRUE, TRUE, TRUE)
)

# Display the data frame
avengers

# Structure of data frame
str(avengers)

# Summary statistics
summary(avengers)

Accessing Data Frame Elements

You can access elements of a data frame in several ways:

1. Using column names with the $ operator:

# Get an entire column
star_wars_chars$name  # Returns c("Luke", "Leia", "Han", "Chewie")

# Get a specific element
star_wars_chars$age[2]  # Returns 19 (Leia's age)

2. Using square brackets [row, column]:

# Get a specific cell (row 2, column 3)
star_wars_chars[2, 3]  # Returns TRUE (Leia's force sensitivity)

# Get multiple rows/columns
star_wars_chars[1:2, c("name", "age")]  # First two characters, name and age only

# Get all rows of a column
star_wars_chars[, "name"]  # All names

# Get all columns for a row
star_wars_chars[2, ]  # All data for Leia

3. Filtering data frames with logical conditions:

# Get rows where age is over 25
star_wars_chars[star_wars_chars$age > 25, ]

# Get rows where character is force sensitive
star_wars_chars[star_wars_chars$force_sensitive == TRUE, ]

# Combine conditions
star_wars_chars[star_wars_chars$species == "Human" & star_wars_chars$force_sensitive == TRUE, ]

Modifying Data Frames

Data frames can be modified after creation:

# Add a new column
star_wars_chars$weapon <- c("Lightsaber", "Blaster", "Blaster", "Bowcaster")

# Change a value
star_wars_chars$age[3] <- 30

# Add a new row
new_character <- data.frame(
  name = "Yoda",
  species = "Unknown",
  force_sensitive = TRUE,
  age = 900,
  weapon = "Lightsaber"
)
star_wars_chars <- rbind(star_wars_chars, new_character)

Exercise 12: Accessing Data Frames

Access and manipulate data frames:

Exercise
Start Over Show Hint
Run Code
# Pre-defined data frame
star_trek_crew <- data.frame(
name = c("Kirk", "Spock", "McCoy", "Uhura", "Scotty"),
role = c("Captain", "Science Officer", "Doctor", "Communications", "Engineer"),
species = c("Human", "Vulcan", "Human", "Human", "Human"),
age = c(35, 40, 38, 32, 45),
stardate_joined = as.Date(c("2265-01-15", "2265-01-15", "2265-02-10",
"2265-01-20", "2265-03-05"))
)
_webr_editor_12 = Object {code: null, options: Object, indicator: it}
Hint

Access data frame columns using $ notation or by specifying rows and columns with [row, column] notation. Filter rows using logical conditions. It’s like accessing the Starfleet database!

Solution: 
# Pre-defined data frame
star_trek_crew <- data.frame(
  name = c("Kirk", "Spock", "McCoy", "Uhura", "Scotty"),
  role = c("Captain", "Science Officer", "Doctor", "Communications", "Engineer"),
  species = c("Human", "Vulcan", "Human", "Human", "Human"),
  age = c(35, 40, 38, 32, 45),
  stardate_joined = as.Date(c("2265-01-15", "2265-01-15", "2265-02-10", 
                         "2265-01-20", "2265-03-05"))
)

# Display the full data frame
star_trek_crew

# Access column by name
star_trek_crew$name

# Access specific rows and columns
star_trek_crew[2, 3]  # Row 2, Column 3 (Spock's species)
star_trek_crew[1:3, c("name", "role")]  # First three crew, name and role only

# Filter data frame
non_humans <- star_trek_crew[star_trek_crew$species != "Human", ]
non_humans

# Calculate average age
mean(star_trek_crew$age)

# Sort data frame by age
star_trek_crew[order(star_trek_crew$age), ]

# Find the oldest crew member
star_trek_crew[which.max(star_trek_crew$age), ]
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