Pipe operator (%>% and |>) in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pipe with dplyr and base R

What is the output of this R code using the pipe operator %>% from dplyr?

R Programming

library(dplyr)
result <- mtcars %>%
  filter(cyl == 6) %>%
  summarise(avg_mpg = mean(mpg)) %>%
  pull(avg_mpg)
print(round(result, 2))

A 19.74

B 20.57

C 21.00

D 18.50

💡 Hint

Look at the cars with 6 cylinders and calculate their average mpg.

The code filters mtcars for 6-cylinder cars, then calculates the mean mpg, which is approximately 19.74.

❓ Predict Output

intermediate

Output of base R pipe |> with nested functions

What is the output of this R code using the base pipe operator |>?

R Programming

result <- 1:5 |> sum() |> sqrt()
print(round(result, 3))

A 2.236

B 5.477

C 15.000

D 3.873

💡 Hint

Sum 1 to 5, then take the square root.

Sum of 1 to 5 is 15, square root of 15 is approximately 3.873.

🔧 Debug

advanced

Identify the error in pipe usage

What error does this R code produce when using the pipe operator %>%?

R Programming

library(dplyr)
result <- mtcars %>%
  filter(cyl == 4) %>%
  summarise(avg_hp = mean(hp)) %>%
  select(avg_hp) %>%
  mean()
print(result)

A Error: no applicable method for 'mean' applied to an object of class 'data.frame'

B Error: argument is not numeric or logical: returning NA

C Error: object of type 'closure' is not subsettable

D No error, prints average horsepower

💡 Hint

Check what class the object is before calling mean().

select(avg_hp) returns a data frame, mean() expects a numeric vector, so it produces "Error: no applicable method for 'mean' applied to an object of class 'data.frame'".

🧠 Conceptual

advanced

Understanding pipe operator behavior

Which statement best describes the difference between %>% and |> in R?

A %>% is deprecated and replaced by |> in all R versions.

B %>% is from magrittr and allows placeholder .; |> is base R pipe introduced in R 4.1 without placeholder support.

C %>% is base R pipe; |> is from magrittr package with more features.

D Both %>% and |> are identical in syntax and behavior.

💡 Hint

Think about package origin and placeholder usage.

%>% comes from magrittr and supports the dot placeholder for the left-hand side; |> is a base R pipe introduced in R 4.1 and does not support the dot placeholder.

❓ Predict Output

expert

Output of complex pipe with anonymous function

What is the output of this R code using the base pipe |> with an anonymous function?

R Programming

result <- 1:4 |> ((x) x * 2)() |> sum()
print(result)

A Error: unexpected '()' in expression

B 10

C 20

D 30

💡 Hint

Anonymous function doubles each element, then sum them.

1:4 is doubled to 2,4,6,8; sum is 20.