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R for Data Analytics MCQ - Data Manipulation with R

16 Which expression selects all columns except the second column from data frame df?

Negative column indices exclude the specified columns.

17 Which function can replace missing values using conditional vectorized logic?

ifelse() performs vectorized conditional replacement.

18 Which function can split a data frame into groups based on a factor?

split() divides data into groups according to a factor or grouping variable.

19 Which function can return the indices that would sort a data frame column without directly sorting the values?

order() returns the permutation of indices needed to sort the values.

20 How can a data frame df be sorted by column score in descending order using base R?

For numeric values, order(-df$score) produces indices in descending order.

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lapply and sapply

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Question:

Which function combines objects side by side as columns?

A. rbind()
B. cbind()
C. merge.rows()
D. stackrows()

Correct answer: B

Explanation:

cbind() combines objects by columns.

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