R Programming Language Certification Data Manipulation & Transformation 2

Question 1

Which tidyr function separates a single column into multiple columns based on a delimiter?

Accepted Answer

separate()

Answer

separate() splits a single character column into multiple columns using a specified separator character.

Question 2

Which dplyr function removes duplicate rows from a data frame?

Accepted Answer

distinct()

Answer

distinct() returns only unique rows from a data frame, optionally based on specified columns.

Question 3

What is the result of left_join(df1, df2, by='id') in dplyr?

Accepted Answer

All rows from df1, matched rows from df2

Answer

left_join() retains all rows from the left data frame (df1) and fills in matched values from df2, leaving NAs for non-matches.

Question 4

Which function in base R applies a function to each element of a list and returns a list?

Accepted Answer

lapply()

Answer

lapply() applies a function to each element of a list and always returns a list of the same length.

Question 5

In dplyr, which function is used to reorder rows based on column values?

Accepted Answer

arrange()

Answer

arrange() reorders the rows of a data frame based on the values of one or more columns, defaulting to ascending order.

R Programming Language Certification Practice Test