1. What is data preprocessing in R?
A) Cleaning and preparing data for analysis
B) Creating new datasets
C) Visualizing data patterns
D) Installing R packages
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2. What is data wrangling?
A) Data visualization
B) Data cleaning and structuring
C) Data storage
D) Data collection
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3. Which function is used to order data in R?
A) sort()
B) arrange()
C) order()
D) rank()
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4. What does filtering data mean in R?
A) Removing all data
B) Sorting data alphabetically
C) Converting data types
D) Selecting rows based on conditions
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5. Which function can be used to filter data frames in R?
A) subset()
B) filter()
C) select()
D) choose()
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6. What does a histogram show in R?
A) Relationship between two variables
B) Distribution of a single variable
C) Time series data
D) Categorical data counts
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7. Which function creates a histogram in R?
A) hist()
B) histogram()
C) plot()
D) bar()
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8. What does a box plot display in R?
A) Mean and standard deviation
B) Correlation coefficients
C) Five-number summary
D) Frequency distribution
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9. Which function creates a box plot in R?
A) box()
B) boxplot()
C) plot()
D) summary()
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10. What type of data is best displayed using bar plots in R?
A) Continuous numerical data
B) Time series data
C) Correlation data
D) Categorical data
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11. Which function creates bar plots in R?
A) barplot()
B) bar()
C) plot()
D) chart()
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12. What is ggplot2 in R?
A) A data manipulation package
B) A data visualization package
C) A statistical testing package
D) A machine learning package
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13. Which function starts a ggplot in R?
A) ggplot()
B) plot()
C) graph()
D) chart()
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14. What does aes() do in ggplot2?
A) Adds titles to plots
B) Creates animations
C) Maps variables to visual properties
D) Saves plots to files
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15. Which geom is used to create scatter plots in ggplot2?
A) geom_line()
B) geom_point()
C) geom_bar()
D) geom_histogram()
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16. What is a QQ plot used for in R?
A) Showing correlations
B) Displaying time series
C) Creating bar charts
D) Checking data distribution normality
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17. Which function creates a QQ plot in base R?
A) qqnorm()
B) qqplot()
C) qq()
D) quantile()
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18. Which function calculates correlation in R?
A) correlation()
B) corr()
C) cor()
D) relate()
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19. Which function performs a t-test in R?
A) ttest()
B) t.test()
C) test.t()
D) student.test()
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20. What does the aggregate() function do in R?
A) Combines data frames
B) Sorts data
C) Filters data
D) Applies functions to grouped data
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21. Which function is used to join data frames in R?
A) merge()
B) join()
C) combine()
D) bind()
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22. What does rbind() do in R?
A) Removes rows
B) Reorders rows
C) Combines data frames by rows
D) Renames rows
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23. What does cbind() do in R?
A) Creates new columns
B) Combines data frames by columns
C) Counts columns
D) Removes columns
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24. What does complete.cases() identify in R?
A) All cases in dataset
B) Incomplete cases
C) Missing values
D) Rows with no missing values
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25. Which function removes missing values in R?
A) na.omit()
B) remove.na()
C) delete.na()
D) drop.na()
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26. What does the scale() function do in R?
A) Resizes plots
B) Measures data size
C) Standardizes variables
D) Scales graphics
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27. Which function converts continuous variables to categorical in R?
A) convert()
B) cut()
C) factor()
D) group()
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28. What does the reshape() function do in R?
A) Changes data types
B) Resizes data frames
C) Removes duplicates
D) Transforms data between wide and long formats
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29. Which function identifies duplicate rows in R?
A) duplicated()
B) duplicate()
C) dup()
D) repeat()
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30. What does the with() function do in R?
A) Creates new objects
B) Removes objects
C) Evaluates expressions within data frame context
D) Combines multiple objects
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31. What does the attach() function do in R?
A) Attaches files to emails
B) Adds data frame to search path
C) Connects to databases
D) Links external libraries
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32. What is the opposite of attach() in R?
A) remove()
B) delete()
C) unload()
D) detach()
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33. Which function is used to modify columns in a data frame?
A) transform()
B) modify()
C) change()
D) alter()
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34. What does the within() function do in R?
A) Checks if values are within range
B) Creates subsets
C) Evaluates and modifies data frame expressions
D) Finds values within groups
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35. What does the by() function do in R?
A) Sorts data
B) Applies functions to data subsets
C) Filters data
D) Groups data
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36. Which function applies functions to vector subsets in R?
A) apply()
B) lapply()
C) sapply()
D) tapply()
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37. What does lapply() return in R?
A) A list
B) A vector
C) A matrix
D) A data frame
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38. What does sapply() do compared to lapply() in R?
A) Works slower
B) Simplifies the result
C) Works with strings only
D) Applies to single elements
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39. What is mapply() used for in R?
A) Creating maps
B) Mapping variables
C) Applying functions to multiple arguments
D) Plotting geographical data
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40. What does the split() function do in R?
A) Separates strings
B) Divides numbers
C) Breaks data frames
D) Divides data into groups
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41. Which function reverses the split() operation in R?
A) unsplit()
B) combine()
C) merge()
D) join()
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42. What does the stack() function do in R?
A) Creates data stacks
B) Piles up data
C) Converts wide data to long format
D) Stacks multiple datasets
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43. Which function reverses the stack() operation in R?
A) destack()
B) unstack()
C) widen()
D) spread()
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44. What does the melt() function do in R?
A) Melts ice data
B) Combines datasets
C) Removes data
D) Transforms wide data to long format
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45. Which function transforms long data to wide format in R?
A) cast()
B) spread()
C) widen()
D) expand()
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46. Which function gets or sets column names in R?
A) columns()
B) names()
C) colnames()
D) headers()
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47. What does rownames() do in R?
A) Counts rows
B) Gets or sets row names
C) Creates new rows
D) Removes rows
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48. Which function returns the number of rows in R?
A) rows()
B) count.rows()
C) length.rows()
D) nrow()
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49. What does ncol() return in R?
A) Number of columns
B) Column names
C) New columns
D) Column types
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50. What does the View() function do in R?
A) Creates views of data
B) Prints data to console
C) Opens data in a viewer window
D) Saves data views
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