Handling missing values (na.rm, na.omit) in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of sum() with na.rm parameter

What is the output of the following R code?

R Programming

x <- c(1, 2, NA, 4)
sum(x, na.rm = TRUE)

A 7

B NA

C Error: missing value

D 6

💡 Hint

The na.rm = TRUE argument tells sum() to ignore missing values.

The sum function adds all numbers ignoring NA when na.rm = TRUE. So 1 + 2 + 4 = 7.

❓ Predict Output

intermediate

Effect of na.omit() on a vector

What is the output of this R code?

R Programming

y <- c(3, NA, 5, NA, 7)
na.omit(y)

A 3 5 7

B 3 NA 5 NA 7

C Error: cannot omit NA

D NA NA NA

💡 Hint

na.omit() removes all NA values from the vector.

na.omit() returns the vector without any NA values, so only 3, 5, and 7 remain.

❓ Predict Output

advanced

Sum of vector with NA without na.rm

What happens when you run this R code?

R Programming

z <- c(10, NA, 20)
sum(z)

A 30

B Error: missing value

C 10

D NA

💡 Hint

sum() returns NA if there is any missing value and na.rm is not TRUE.

Without na.rm = TRUE, sum() returns NA if any element is NA.

🧠 Conceptual

advanced

Behavior of na.omit() on data frame

Given the data frame below, what will na.omit(df) return?

R Programming

df <- data.frame(a = c(1, NA, 3), b = c(NA, 2, 3))
na.omit(df)

A Rows with NA in column 'a' removed, but rows with NA in 'b' kept

B All rows kept because na.omit only works on vectors

C Rows with any NA values removed, so only the last row remains

D Error: na.omit cannot be applied to data frames

💡 Hint

na.omit removes any row with at least one NA in any column.

na.omit removes rows with any missing values, so only the row with no NAs remains.

❓ Predict Output

expert

Count of non-NA elements using sum and is.na

What is the output of this R code?

R Programming

v <- c(NA, 4, NA, 7, 9)
sum(!is.na(v))

A 2

B 3

C NA

D Error: invalid argument

💡 Hint

is.na(v) returns TRUE for NA values, !is.na(v) is TRUE for non-NA values, sum counts TRUE as 1.

There are 3 non-NA values (4, 7, 9), so sum(!is.na(v)) returns 3.