Multiple Choices: Data Wrangling without dplyr part 2

Questions

1. How do you combine two data frames vertically in base R?

cbind() merge() rbind() paste()

2. Which function is used to remove rows with missing values in base R?

omit.na() na.omit() na.remove() drop.na()

3. If you want to select specific columns from a data frame, which function can you use?

select() subset() pick() choose()

4. Which function would you use to create a new variable in a data frame based on existing columns?

transform() mutate() add() new_var()

5. Which of the following can be used to sort a data frame by a specific column in base R?

order() sort() rank() arrange()

6. When you want to filter rows based on conditions in base R, which function should you use?

select() filter() subset() where()

7. What function can you use to find the mean of each column in a data frame?

mean() colMeans() apply() rowMeans()

8. Which function allows you to summarize a data frame by calculating statistics like mean, median, or sum for each group of a factor variable?

aggregate() summarize() group_by() tapply()

9. Which function in base R is commonly used to combine two data frames by a common column?

merge() cbind() join() rbind()

10. How can you change the name of a specific column in a data frame in base R?

names(data)[column_index] <- "new_name" rename() colnames(data)[column_index] <- "new_name" Both A and C

11. Which function can be used to get the structure of a data frame, including column names, data types, and a preview of data?

str() summary() view() structure()

12. To add a new row to a data frame in base R, which function would you use?

append() rbind() cbind() add_row()

13. What is the purpose of the apply() function in base R?

It applies a function to each row in a matrix or data frame. It applies a function to each column in a matrix or data frame. It applies a function across rows or columns in a matrix or data frame. It is used to merge data frames.

14. Which function is used to count the number of rows in a data frame?

length() dim() nrow() rows()

15. If you want to rename multiple columns in a data frame, which command should you use?

colnames(data) <- c("new_name1", "new_name2", ...) rename() names(data) <- c("new_name1", "new_name2", ...) Both A and C

16. What function would you use to convert a specific column in a data frame to a factor?

as.factor() factor() to.factor() Both A and B

17. Which function can be used to transpose a data frame in base R?

flip() rotate() t() transpose

18. If you want to create a subset of a data frame based on multiple conditions, which operator can help combine these conditions?

| (OR) & (AND) + (ADD) * (MULTIPLY)

19. Which base R function returns the number of unique values in a column?

unique() distinct() length(unique()) length()

20. How do you remove a column from a data frame in base R?

data$column_name <- NULL remove(data$column_name) drop(data, column_name) delete(data$column_name)

21. Which function in base R can you use to split a data frame by a factor or categorical variable?

cut() split() group() separate()

22. How do you remove duplicate rows from a data frame in base R?

unique() distinct() remove_duplicates() duplicates()

23. Which function can calculate the sum of each row in a matrix or data frame?

rowSums() apply() sum() colSums()

24. To extract specific rows and columns in a data frame by index position, you would use:

data[row, column] subset() extract() select()

25. Which function in base R will give a summary of each column, including mean, median, and quartiles?

describe() summary() aggregate() report()

26. What function can you use to find the maximum value in each column of a data frame?

max() colMaxs() apply(data, 2, max) summarize()

27. How do you add a prefix to all column names in a data frame in base R?

colnames(data) <- paste0("prefix_", colnames(data)) names(data) <- "prefix_" + colnames(data) rename(data, prefix) add_prefix()

28. Which function can be used to convert a data frame to a matrix in base R?

as.matrix() matrix() convert_to_matrix() data.matrix()

29. To replace all occurrences of a specific value in a data frame column, you would use:

data$column[data$column == value] <- new_value replace(data$column, value, new_value) swap(data$column, value, new_value) change_value()

30. Which function would you use to combine multiple character vectors into a single string in base R?

combine() paste() merge() concatenate()