1 Intro to basics

1.1 How it works

In the text editor you should type R code to solve the exercises. When you hit ctrl + enter, every line of code is interpreted and executed by R and you get a message whether or not your code was correct.

R makes use of the # sign to add comments, so that you and others can understand what the R code is about. Comments are not run as R code, so they will not influence your result. For example, Calculate 3 + 4 in the editor on the right is a comment.

You can also execute R commands straight in the console. This is a good way to experiment with R code.

Instructions `100 XP`

- In the text editor on the right there is already some sample code. 
- Can you see which lines are actual R code and which are comments?
- Add a line of code that calculates the sum of 6 and 12, 
    and hit the enter button

ex_01.R

# Calculate 3 + 4
3 + 4
# Calculate 6 + 12
6 + 12

1.2 Arithmetic with R

In its most basic form, R can be used as a simple calculator. Consider the following arithmetic operators:

Addition: +
Subtraction: -
Multiplication: *
Division: /
Exponentiation: ^
Modulo: %%

The last two might need some explaining:

The ^ operator raises the number to its left to the power of the number to its right: for example 3^2 is 9.
The modulo returns the remainder of the division of the number to the left by the number on its right, for example 5 modulo 3 or 5 %% 3 is 2.

Instructions `100 XP`

- Type 2^5 in the editor to calculate 2 to the power 5.
- Type 28 %% 6 to calculate 28 modulo 6.
- Run the answer in the console and have a look at the R output .
- Note how the # symbol is used to add comments on the R code.

ex_02.R

# An addition
5 + 5 

# A subtraction
5 - 5 

# A multiplication
3 * 5
    # A division
(5 + 5) / 2 
# Exponentiation
2 ^ 5
# Modulo
28 %% 6

1.2.1 Variable assignment

A basic concept in (statistical) programming is called a variable.

A variable allows you to store a value (e.g. 4) or an object (e.g. a function description) in R. You can then later use this variable’s name to easily access the value or the object that is stored within this variable.

You can assign a value 4 to a variable my_var with the command

my_var <- 4

1.2.1.1 Instructions `100 XP`

Over to you: complete the code in the editor such that it assigns the value 42 to the variable x in the editor. Submit the answer. Notice that when you ask R to print x, the value 42 appears.

ex_03.R

# Assign the value 42 to x
x <- 42
# Print out the value of the variable x
print (x)

1.2.2 Variable assignment (2)

Suppose you have a fruit basket with five apples. As a data analyst in training, you want to store the number of apples in a variable with the name my_apples.

1.2.2.1 Instructions `100 XP`

Type the following code in the editor: my_apples <- 5. This will assign the value 5 to my_apples.
Type: my_apples below the second comment. This will print out the value of my_apples.
Run your answer, and look at the output: you see that the number 5 is printed. So R now links the variable my_apples to the value 5.

ex_04.R

# Assign the value 5 to the variable my_apples
my_apples <- 5
# Print out the value of the variable my_apples
print(my_apples)

1.3 Variable assignment (3)

Every tasty fruit basket needs oranges, so you decide to add six oranges. As a data analyst, your reflex is to immediately create the variable my_oranges and assign the value 6 to it. Next, you want to calculate how many pieces of fruit you have in total. Since you have given meaningful names to these values,

you can now code this in a clear way:

my_apples + my_oranges

Instructions `100 XP`

Assign to my_oranges the value 6.
Add the variables my_apples and my_oranges and have R simply print the result.
Assign the result of adding my_apples and my_oranges to a new variable my_fruit.

ex_05.R

# Assign a value to the variables my_apples and my_oranges
my_apples <- 5
my_oranges <- 6

# Add these two variables together
my_apples + my_oranges

# Create the variable my_fruit
my_fruit <- my_apples + my_oranges

1.4 Apples and oranges

Common knowledge tells you not to add apples and oranges. But hey, that is what you just did, no :-)? The my_apples and my_oranges variables both contained a number in the previous exercise. The + operator works with numeric variables in R. If you really tried to add “apples” and “oranges”, and assigned a text value to the variable my_oranges (see the editor), you would be trying to assign the addition of a numeric and a character variable to the variable my_fruit. This is not possible.

Instructions `100 XP`

Run the answer and read the error message. Make sure to understand why this did not work.
Adjust the code so that R knows you have 6 oranges and thus a fruit basket with 11 pieces of fruit.

ex_06.R

# Assign a value to the variable my_apples
my_apples <- 5 
# Fix the assignment of my_oranges
my_oranges <- "six" 
# Create the variable my_fruit and print it out
my_fruit <- my_apples + my_oranges 
my_fruit

Response

ex_06.R

# Assign a value to the variable my_apples
my_apples <- 5 
# Fix the assignment of my_oranges
my_oranges <- 6 
# Create the variable my_fruit and print it out
my_fruit <- my_apples + my_oranges 
my_fruit

1.5 Basic data types in R

R works with numerous data types. Some of the most basic types to get started are:

Decimal values like 4.5 are called numerics.
Whole numbers like 4 are called integers. Integers are also numerics.
Boolean values (TRUE or FALSE) are called logical.
Text (or string) values are called characters.

Note how the quotation marks in the editor indicate that “some text” is a string.

Instructions `100 XP`

Change the value of the:

my_numeric variable to 42.
my_character variable to "universe". Note that the quotation marks indicate that “universe” is a character.
my_logical variable to FALSE.

Note that R is case sensitive!

Thus despite the varibales called var, Var, vAr, has the same fonetic characters, R understand each of these as different memory addresses.

ex_07.R

# Change my_numeric to be 42
my_numeric <- 42.5

# Change my_character to be "universe"
my_character <- "some text"

# Change my_logical to be FALSE
my_logical <- TRUE

Response

ex_07.R

# Change my_numeric to be 42
my_numeric <- 42

# Change my_character to be "universe"
my_character <- "universe"

# Change my_logical to be FALSE
my_logical <- FALSE

1.6 What’s that data type?

Do you remember that when you added 5 + “six”, you got an error due to a mismatch in data types? You can avoid such embarrassing situations by checking the data type of a variable beforehand. You can do this with the class() function, as the code in the editor shows.

Instructions `100 XP`

Complete the code in the editor and also print out the classes of my_character and my_logical.

ex_08.R

# Declare variables of different types

my_numeric <- 42
my_character <- "universe"
my_logical <- FALSE 
# Check class of my_numeric
class(my_numeric)

# Check class of my_character
class(my_character)

# Check class of my_logical
class(my_logical)

--- format: html: highlight-style: dracula code-line-numbers: true code-block-border-left: true code-tools: source: true toggle: false caption: none --- # Intro to basics {.numbered} ## How it works In the text editor you should type R code to solve the exercises. When you hit **ctrl + enter**, every line of code is interpreted and executed by R and you get a message whether or not your code was correct. R makes use of the # sign to add comments, so that you and others can understand what the R code is about. Comments are not run as R code, so they will not influence your result. For example, Calculate 3 + 4 in the editor on the right is a comment. You can also execute R commands straight in the console. This is a good way to experiment with R code. ### Instructions `100 XP` {.unnumbered} - In the text editor on the right there is already some sample code. - Can you see which lines are actual R code and which are comments? - Add a line of code that calculates the sum of 6 and 12, and hit the enter button ```{.R filename="ex_01.R"} # Calculate 3 + 4 3 + 4 # Calculate 6 + 12 6 + 12 ``` ## Arithmetic with R In its most basic form, R can be used as a simple calculator. Consider the following arithmetic operators: - Addition: `+` - Subtraction: `-` - Multiplication: `*` - Division: `/` - Exponentiation: `^` - Modulo: `%%` The last two might need some explaining: * The `^` operator raises the number to its left to the power of the number to its right: for example `3^2` is 9. * The modulo returns the remainder of the division of the number to the left by the number on its right, for example 5 modulo 3 or `5 %% 3` is 2. ### Instructions `100 XP` {.unnumbered} - Type 2^5 in the editor to calculate 2 to the power 5. - Type 28 %% 6 to calculate 28 modulo 6. - Run the answer in the console and have a look at the R output . - Note how the # symbol is used to add comments on the R code. ```{.R filename="ex_02.R"} # An addition 5 + 5 # A subtraction 5 - 5 # A multiplication 3 * 5 # A division (5 + 5) / 2 # Exponentiation 2 ^ 5 # Modulo 28 %% 6 ``` ### Variable assignment A basic concept in (statistical) programming is called a variable. A variable allows you to store a value (e.g. 4) or an object (e.g. a function description) in R. You can then later use this variable's name to easily access the value or the object that is stored within this variable. ::: {.callout-tip} ## You can assign a value 4 to a variable my_var with the command > my_var <- 4 ::: #### Instructions `100 XP` Over to you: complete the code in the editor such that it assigns the value 42 to the variable x in the editor. Submit the answer. Notice that when you ask R to print x, the value 42 appears. ```{.r filename="ex_03.R"} # Assign the value 42 to x x <- 42 # Print out the value of the variable x print (x) ``` ### Variable assignment (2) Suppose you have a fruit basket with five apples. As a data analyst in training, you want to store the number of apples in a variable with the name my_apples. #### Instructions `100 XP` * Type the following code in the editor: my_apples <- 5. This will assign the value 5 to my_apples. * Type: my_apples below the second comment. This will print out the value of my_apples. * Run your answer, and look at the output: you see that the number 5 is printed. So R now links the variable my_apples to the value 5. ```{.r filename="ex_04.R"} # Assign the value 5 to the variable my_apples my_apples <- 5 # Print out the value of the variable my_apples print(my_apples) ``` ## Variable assignment (3) Every tasty fruit basket needs oranges, so you decide to add six oranges. As a data analyst, your reflex is to immediately create the variable my_oranges and assign the value 6 to it. Next, you want to calculate how many pieces of fruit you have in total. Since you have given meaningful names to these values, ::: {.callout-note} ## you can now code this in a clear way: my_apples + my_oranges ::: ### Instructions `100 XP` {.unnumbered} * Assign to my_oranges the value 6. * Add the variables my_apples and my_oranges and have R simply print the result. * Assign the result of adding my_apples and my_oranges to a new variable my_fruit. ```{.r filename="ex_05.R"} # Assign a value to the variables my_apples and my_oranges my_apples <- 5 my_oranges <- 6 # Add these two variables together my_apples + my_oranges # Create the variable my_fruit my_fruit <- my_apples + my_oranges ``` ## Apples and oranges Common knowledge tells you not to add apples and oranges. But hey, that is what you just did, no :-)? The my_apples and my_oranges variables both contained a number in the previous exercise. The + operator works with numeric variables in R. If you really tried to add "apples" and "oranges", and assigned a text value to the variable my_oranges (see the editor), you would be trying to assign the addition of a numeric and a character variable to the variable my_fruit. This is not possible. ### Instructions `100 XP` {.unnumbered} * Run the answer and read the error message. Make sure to understand why this did not work. * Adjust the code so that R knows you have 6 oranges and thus a fruit basket with 11 pieces of fruit. ```{.r filename="ex_06.R"} # Assign a value to the variable my_apples my_apples <- 5 # Fix the assignment of my_oranges my_oranges <- "six" # Create the variable my_fruit and print it out my_fruit <- my_apples + my_oranges my_fruit ``` Response ```{.r filename="ex_06.R"} # Assign a value to the variable my_apples my_apples <- 5 # Fix the assignment of my_oranges my_oranges <- 6 # Create the variable my_fruit and print it out my_fruit <- my_apples + my_oranges my_fruit ``` ## Basic data types in R R works with numerous data types. Some of the most basic types to get started are: * Decimal values like 4.5 are called numerics. * Whole numbers like 4 are called integers. Integers are also numerics. * Boolean values (TRUE or FALSE) are called logical. * Text (or string) values are called characters. Note how the quotation marks in the editor indicate that "some text" is a string. ## Instructions `100 XP` {.unnumbered} Change the value of the: * `my_numeric` variable to 42. * `my_character` variable to `"universe"`. Note that the quotation marks indicate that "universe" is a character. * `my_logical` variable to `FALSE`. ::: {.callout-note} ## Note that R is case sensitive! Thus despite the varibales called `var`, `Var`, `vAr`, has the same fonetic characters, R understand each of these as different memory addresses. ::: ```{.r filename="ex_07.R"} # Change my_numeric to be 42 my_numeric <- 42.5 # Change my_character to be "universe" my_character <- "some text" # Change my_logical to be FALSE my_logical <- TRUE ``` Response ```{.r filename="ex_07.R"} # Change my_numeric to be 42 my_numeric <- 42 # Change my_character to be "universe" my_character <- "universe" # Change my_logical to be FALSE my_logical <- FALSE ``` ## What's that data type? Do you remember that when you added 5 + "six", you got an error due to a mismatch in data types? You can avoid such embarrassing situations by checking the data type of a variable beforehand. You can do this with the class() function, as the code in the editor shows. ### Instructions `100 XP` {.unnumbered} Complete the code in the editor and also print out the classes of my_character and my_logical. ```{.r filename=ex_08.R} # Declare variables of different types my_numeric <- 42 my_character <- "universe" my_logical <- FALSE # Check class of my_numeric class(my_numeric) # Check class of my_character class(my_character) # Check class of my_logical class(my_logical) ```

1.1 How it works

Instructions 100 XP

1.2 Arithmetic with R

Instructions 100 XP

1.2.1 Variable assignment

1.2.1.1 Instructions 100 XP

1.2.2 Variable assignment (2)

1.2.2.1 Instructions 100 XP

1.3 Variable assignment (3)

Instructions 100 XP

1.4 Apples and oranges

Instructions 100 XP

1.5 Basic data types in R

Instructions 100 XP

1.6 What’s that data type?

Instructions 100 XP

Instructions `100 XP`

Instructions `100 XP`

1.2.1.1 Instructions `100 XP`

1.2.2.1 Instructions `100 XP`

Instructions `100 XP`

Instructions `100 XP`

Instructions `100 XP`

Instructions `100 XP`