R Programming Language Certification Data Manipulation & Tidyverse in R 3

Question 1

Which R package provides tools for working with strings, including pattern matching and string manipulation?

Accepted Answer

stringr

Answer

stringr provides consistent, easy-to-use string functions (str_detect, str_replace, str_split, etc.) built on top of stringi.

Question 2

Which R function checks for missing values (NA) in a vector?

Accepted Answer

is.na()

Answer

is.na() returns a logical vector of the same length as the input, with TRUE where values are NA.

Question 3

Which dplyr function removes duplicate rows from a data frame?

Accepted Answer

distinct()

Answer

distinct() returns unique rows from a data frame, optionally specifying which columns to check for uniqueness.

Question 4

In R, what does the function n() return when used inside summarise()?

Accepted Answer

The number of rows in each group

Answer

n() is a dplyr context function that returns the number of observations in the current group when used within summarise() or mutate().

Question 5

Which R package provides the map() family of functions for applying a function to each element of a list or vector?

Accepted Answer

purrr

Answer

purrr's map() functions (map(), map_dbl(), map_chr(), etc.) provide type-safe alternatives to base R's lapply()/sapply().

R Programming Language Certification Practice Test