Numeric type in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a numeric variable with value 10.

R Programming

num <- [1]

Drag options to blanks, or click blank then click option'

Ac(10)

B"10"

CTRUE

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around the number, which makes it a string.

Using TRUE which is logical, not numeric.

The number 10 is assigned directly as a numeric value without quotes.

2fill in blank

medium

Complete the code to check if variable x is numeric.

R Programming

is.numeric([1])

Drag options to blanks, or click blank then click option'

Ax

B10

C"x"

DTRUE

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the variable name as a string.

Passing a literal number instead of the variable.

Use the variable name without quotes to check its type.

3fill in blank

hard

Fix the error in the code to convert a string to numeric.

R Programming

num <- as.numeric([1])

Drag options to blanks, or click blank then click option'

ATRUE

Bnum

C"10"

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a numeric value directly to as.numeric().

Passing a logical value instead of a string.

Use a string "10" to convert it to numeric with as.numeric().

4fill in blank

hard

Fill both blanks to create a numeric vector and check its type.

R Programming

vec <- c([1], [2])
is.numeric(vec)

Drag options to blanks, or click blank then click option'

A5

B"5"

C10

D"10"

Attempts:

3 left

💡 Hint

Common Mistakes

Using quoted numbers which create character vectors.

Mixing numeric and character values in the vector.

Use numeric values 5 and 10 without quotes to create a numeric vector.

5fill in blank

hard

Fill all three blanks to create a numeric vector, convert a string to numeric, and check types.

R Programming

vec <- c([1], [2])
num <- as.numeric([3])
is.numeric(vec) && is.numeric(num)

Drag options to blanks, or click blank then click option'

A3

B"7"

Attempts:

3 left

💡 Hint

Common Mistakes

Using quoted numbers in the vector.

Passing numeric values directly to as.numeric() unnecessarily.

Use numeric values 3 and 3 for the vector, convert string "7" to numeric.

Practice

1. Which of the following is TRUE about numeric types in R?

easy

A. Numeric and integer types are the same in R.

B. Integer type stores decimal numbers by default.

C. Numeric type stores decimal numbers by default.

D. You must always use quotes to create numeric values.

Solution

1. Step 1: Understand numeric and integer types in R

   In R, numeric type stores decimal numbers by default, while integer type stores whole numbers with an L suffix.

2. Step 2: Evaluate each option

   Numeric type stores decimal numbers by default correctly states that numeric stores decimals by default. Options A, B, and C are incorrect based on R's type system.

3. Final Answer:

   Numeric type stores decimal numbers by default. -> Option C

4. Quick Check:

   Numeric = decimals [OK]

Hint: Remember: numeric = decimals, integer = whole numbers [OK]

Common Mistakes:

• Confusing integer and numeric types
• Thinking quotes are needed for numbers
• Assuming numeric and integer are identical

2. Which of the following is the correct way to create an integer value 5 in R?

easy

A. x <- 5L

B. x <- "5"

C. x <- 5

D. x <- as.integer("5L")

Solution

1. Step 1: Recall integer creation syntax in R

   In R, to create an integer literal, you add L after the number, e.g., 5L.

2. Step 2: Check each option

   x <- 5L uses 5L which is correct. x <- 5 creates a numeric (decimal) 5, not integer. x <- "5" creates a string. x <- as.integer("5L") fails to convert the string "5L" to integer due to the L suffix, resulting in NA.

3. Final Answer:

   x <- 5L -> Option A

4. Quick Check:

   Integer literal = number + L [OK]

Hint: Use L suffix to make integers, else numeric by default [OK]

Common Mistakes:

• Using plain numbers for integers
• Confusing strings with numbers
• Using as.integer on decimals expecting exact integer

3. What is the output of the following R code?

x <- as.numeric("3.14")
typeof(x)

medium

A. "double"

B. "numeric"

C. "integer"

D. "character"

Solution

1. Step 1: Understand as.numeric() conversion

   as.numeric() converts a string to a numeric type, which in R is stored as double precision floating point.

2. Step 2: Check typeof() result for numeric

   typeof() returns "double" for numeric values with decimals in R.

3. Final Answer:

   "double" -> Option A

4. Quick Check:

   as.numeric() returns double type [OK]

Hint: as.numeric() returns double type, not integer [OK]

Common Mistakes:

• Expecting integer type from as.numeric()
• Confusing character and numeric types
• Thinking numeric means integer

4. Identify the error in this R code:

y <- 10L
z <- "abc"
sum <- y + z

medium

A. Error because sum is a reserved word

B. No error, sum is 10

C. Error because 10L is not numeric

D. Error because "abc" cannot convert to numeric

Solution

1. Step 1: Check addition of integer and character

   z <- "abc" creates a character value. Adding integer y (10L) and character z causes an error because character cannot be converted to numeric for arithmetic operations.

2. Step 2: Confirm the error

   The error is 'non-numeric argument to binary operator' since "abc" cannot convert to numeric.

3. Final Answer:

   Error because "abc" cannot convert to numeric -> Option D

4. Quick Check:

   String in arithmetic causes error [OK]

Hint: Non-numeric strings to as.numeric() produce NA [OK]

Common Mistakes:

• Trying to perform arithmetic on strings
• Thinking 10L is not numeric
• Assuming sum is reserved and causes error

5. You have a character vector c("1", "2.5", "3L", "four"). Which R code correctly converts only the valid numeric values to numeric type, ignoring invalid ones?

hard

A. as.numeric(c("1", "2.5", "3L", "four"))

B. as.numeric(gsub("L", "", c("1", "2.5", "3L", "four")))

C. suppressWarnings(as.numeric(c("1", "2.5", "3L", "four")))

D. as.integer(c("1", "2.5", "3L", "four"))

Solution

1. Step 1: Understand the problem with "3L" and "four"

   "3L" is not directly numeric because of the L suffix as a string; "four" is invalid.

2. Step 2: Use gsub to remove "L" and convert

   Removing "L" from strings allows as.numeric() to convert "3" correctly; "four" becomes NA.

3. Step 3: Check options

   as.numeric(gsub("L", "", c("1", "2.5", "3L", "four"))) removes "L" before conversion, correctly converting valid numbers and producing NA for "four". Others either do not handle "3L" or convert incorrectly.

4. Final Answer:

   as.numeric(gsub("L", "", c("1", "2.5", "3L", "four"))) -> Option B

5. Quick Check:

   Remove non-numeric chars before conversion [OK]

Hint: Remove non-numeric chars before as.numeric() [OK]

Common Mistakes:

• Trying to convert strings with letters directly
• Using as.integer on decimals
• Ignoring warnings from invalid conversions