Integer type in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an integer type in R?

An integer type in R is a data type used to store whole numbers without decimal points. It is different from numeric (double) which can store decimal numbers.

beginner

How do you create an integer in R?

You create an integer in R by adding an L suffix to a number, for example: 5L creates an integer 5.

intermediate

What is the difference between 5 and 5L in R?

5 is a numeric (double) type by default, while 5L is an integer type. They behave differently in some operations and use different memory.

beginner

How can you check if a variable is an integer in R?

Use the function is.integer(x). It returns TRUE if x is an integer type, otherwise FALSE.

intermediate

Why might you want to use integer type instead of numeric in R?

Using integer type can save memory and improve performance when you only need whole numbers. It also helps avoid unexpected decimal calculations.

How do you explicitly create an integer value 10 in R?

A 10L

B 10.0

C "10"

D as.numeric(10)

Adding L after a number like 10L creates an integer in R.

What does the function is.integer(5) return in R?

A FALSE

B TRUE

C Error

D NA

5 is numeric (double) by default, so is.integer(5) returns FALSE.

Which of these is NOT a characteristic of integer type in R?

A Uses less memory than numeric

B Stores whole numbers

C Can store decimal numbers

D Created by adding L suffix

Integer type cannot store decimal numbers; that is for numeric type.

What will typeof(5L) return in R?

A "numeric"

B "integer"

C "double"

D "character"

5L is an integer, so typeof(5L) returns "integer".

Why might you choose integer type over numeric in R?

A To store decimal numbers

B To perform string operations

C To convert strings to numbers

D To save memory when storing whole numbers

Integer type uses less memory and is efficient for whole numbers.

Explain how to create and check an integer type variable in R.

Think about how R treats numbers by default and how to specify integer.

Describe the difference between numeric and integer types in R and why it matters.

Consider how numbers are stored and used in calculations.

Practice

1. What does adding L after a number in R do?

easy

A. It makes the number an integer type.

B. It converts the number to a character string.

C. It makes the number a decimal (double) type.

D. It comments out the number in the code.

Solution

1. Step 1: Understand the role of L in R

   In R, adding L after a number explicitly marks it as an integer type instead of the default double (decimal) type.

2. Step 2: Compare with other types

   Without L, numbers are treated as doubles. Adding L ensures the number is stored as an integer.

3. Final Answer:

   It makes the number an integer type. -> Option A

4. Quick Check:

   Number + L = Integer type [OK]

Hint: Remember: number + L means integer in R [OK]

Common Mistakes:

• Thinking L converts to string
• Assuming numbers are integers by default
• Confusing L with a comment

2. Which of the following is the correct way to create an integer value 10 in R?

easy

A. 10.0

B. as.integer("ten")

C. 10L

D. "10"

Solution

1. Step 1: Identify integer syntax in R

   In R, appending L to a number creates an integer literal, so 10L is an integer 10.

2. Step 2: Check other options

   10.0 is a double, "10" is a string, and as.integer("ten") will cause an error because "ten" is not numeric.

3. Final Answer:

   10L -> Option C

4. Quick Check:

   10L creates integer 10 [OK]

Hint: Use L after number for integer, not quotes or decimals [OK]

Common Mistakes:

• Using decimal like 10.0 instead of 10L
• Putting number in quotes to make integer
• Trying to convert non-numeric string to integer

3. What is the output of this R code?

x <- 5L
typeof(x)

medium

A. "double"

B. "integer"

C. "numeric"

D. "character"

Solution

1. Step 1: Understand the variable assignment

   The variable x is assigned 5L, which is an integer literal in R.

2. Step 2: Use typeof() function

   The typeof() function returns the internal type of the object. Since x is an integer, it returns "integer".

3. Final Answer:

   "integer" -> Option B

4. Quick Check:

   typeof(5L) = "integer" [OK]

Hint: typeof(5L) returns "integer" not "double" [OK]

Common Mistakes:

• Assuming 5L is double type
• Confusing typeof() with class()
• Expecting numeric instead of integer

4. Identify the error in this R code:

num <- 7
int_num <- numL

medium

A. Missing L after 7 to make integer

B. Cannot assign numeric to integer variable

C. Syntax error due to missing comma

D. Variable numL is not defined

Solution

1. Step 1: Check variable names

   The code tries to assign numL to int_num, but numL is not defined anywhere.

2. Step 2: Understand the error type

   This causes an error because R cannot find the variable numL. The correct way to make num integer is 7L, but here the error is undefined variable.

3. Final Answer:

   Variable numL is not defined -> Option D

4. Quick Check:

   Undefined variable causes error [OK]

Hint: Check variable names carefully for typos [OK]

Common Mistakes:

• Assuming numL is a valid variable
• Thinking missing L after 7 causes error here
• Ignoring undefined variable errors

5. You have a vector v <- c(1, 2, 3). How do you convert all elements to integers efficiently?

hard

A. v <- as.integer(v)

B. v <- c(1L, 2L, 3L)

C. v <- as.character(v)

D. v <- as.numeric(v)

Solution

1. Step 1: Understand the vector type

   The vector v is numeric (double) by default because numbers have no L suffix.

2. Step 2: Convert vector elements to integer

   Using as.integer(v) converts all elements to integer type efficiently without rewriting the vector manually.

3. Final Answer:

   v <- as.integer(v) -> Option A

4. Quick Check:

   Use as.integer() to convert vector elements [OK]

Hint: Use as.integer() to convert numeric vectors to integer [OK]

Common Mistakes:

• Manually rewriting vector with L suffix
• Using as.character() which converts to strings
• Using as.numeric() which keeps double type