R Programming Language Certification Data Manipulation & Transformation 3

Question 1

Which function computes summary statistics for each group after group_by()?

Accepted Answer

summarise()

Answer

aggregate()

Answer

collapse()

Answer

reduce()

Question 2

What does the spread() function in tidyr (deprecated) do?

Accepted Answer

Converts long format to wide format

Answer

Removes duplicate values

Answer

Merges two data frames

Answer

Adds missing rows

Question 3

Which function in the purrr package applies a function to each element of a list and returns an atomic vector?

Accepted Answer

map_dbl()

Answer

map()

Answer

walk()

Answer

reduce()

Question 4

In R, which function converts a data frame column to a factor?

Accepted Answer

as.factor()

Answer

as.character()

Answer

to_factor()

Answer

make.factor()

Question 5

Which dplyr function selects rows based on a condition?

Accepted Answer

filter()

Answer

select()

Answer

slice()

Answer

keep()

Question 6

What does the complete() function in tidyr do?

Accepted Answer

Adds rows for missing combinations of variables

Answer

Fills NA values with previous row values

Answer

Removes incomplete cases

Answer

Validates data types in each column