R Programming Language Certification Data Manipulation & Tidyverse in R 2

Question 1

Which tidyr function converts data from wide format to long format?

Accepted Answer

pivot_longer()

Answer

pivot_longer() (tidyr) transforms multiple columns into key-value pairs, converting wide data to long/tidy format.

Question 2

Which dplyr join function keeps all rows from the left data frame and matching rows from the right?

Accepted Answer

left_join()

Answer

left_join() retains all rows from the left table and fills NA for non-matching rows from the right table.

Question 3

Which R function reads a CSV file into a data frame using the readr package?

Accepted Answer

read_csv()

Answer

readr's read_csv() reads delimited files faster than base R's read.csv() and returns a tibble with better default behavior.

Question 4

What is a tibble in R?

Accepted Answer

A modern version of a data frame with better printing and stricter behavior

Answer

A tibble (tbl_df) is a tidyverse-enhanced data frame that prints cleanly, never converts strings to factors by default, and gives clearer error messages.

Question 5

Which dplyr function selects specific columns from a data frame by name or condition?

Accepted Answer

select()

Answer

select() chooses columns by name, position, or helper functions like starts_with(), ends_with(), and contains().

R Programming Language Certification Practice Test

R Programming Language Certification Practice Test

R Programming Language Certification Data Manipulation & Tidyverse in R 2