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

filter()

Answer

mutate()

Answer

arrange()

Question 2

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

Accepted Answer

pivot_longer()

Answer

spread()

Answer

pivot_wider()

Answer

gather_cols()

Question 3

What does the dplyr function group_by() do?

Accepted Answer

Groups rows for subsequent summarise operations

Answer

Sorts rows by a column

Answer

Removes duplicate rows

Answer

Merges two data frames

Question 4

Which operator is used to chain dplyr operations in R?

Accepted Answer

%>%

Answer

->

Answer

+

Answer

::

Question 5

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

Accepted Answer

mutate()

Answer

filter()

Answer

summarise()

Answer

rename()

Question 6

What does the na.omit() function do in R?

Accepted Answer

Removes all rows containing NA values

Answer

Replaces NA values with zero

Answer

Counts NA values in each column

Answer

Converts NA to empty string