R Programming Language Certification Data Manipulation & Transformation

Question 1

Which dplyr function is used to select specific columns from a data frame?

Accepted Answer

select()

Answer

The select() function in dplyr is used to choose specific columns from a data frame by name or index.

Question 2

Which function from tidyr converts a wide-format data frame to long format?

Accepted Answer

pivot_longer()

Answer

pivot_longer() from tidyr reshapes data from wide to long format by stacking multiple columns into key-value pairs.

Question 3

What does the dplyr function group_by() do?

Accepted Answer

Groups rows for subsequent summarise operations

Answer

group_by() defines groups within a data frame so that subsequent operations like summarise() are applied to each group separately.

Question 4

Which operator is used to chain dplyr operations in R?

Accepted Answer

%>%

Answer

The pipe operator %>% (from magrittr/dplyr) passes the left-hand result as the first argument to the right-hand function.

Question 5

Which function would you use to add a new computed column to a data frame in dplyr?

Accepted Answer

mutate()

Answer

mutate() adds new columns to a data frame, often computed from existing columns, without removing any existing columns.

R Programming Language Certification Practice Test