Integer type in R Programming

Introduction

Integers are whole numbers without decimals. They help us count or measure things exactly.

When you need to count items like apples or books.

When you want to store ages or years.

When you want to use numbers without fractions in calculations.

When you want to save memory by using whole numbers only.

Syntax

R Programming

x <- 5L

The L after the number tells R this is an integer.

Without L, numbers are treated as double (decimal) by default.

Examples

This creates an integer 10 and checks its type.

R Programming

a <- 10L
class(a)

This creates a decimal number 3.5, which is not an integer.

R Programming

b <- 3.5
class(b)

This converts the number 7 to an integer type.

R Programming

c <- as.integer(7)
class(c)

Sample Program

This program creates an integer variable x with value 12, prints it, and then prints its type.

R Programming

x <- 12L
print(x)
print(class(x))

Important Notes

Adding L after a number is the easiest way to make it an integer in R.

Integers use less memory than decimal numbers.

Be careful: dividing integers can result in decimals.

Summary

Integers are whole numbers without decimals.

Use L after a number to make it an integer in R.

Integers are useful for counting and exact values.

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