Microsoft Analyzing Big Data with Microsoft R - 070-773 Exam Practice Test

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You use dplyrXdf, and you discover that after you exit the session, the output files that were created were deleted.
You need to prevent the files from being deleted.
Solution: You use dplyrXdf with the persist verb.
Does this meet the goal?

Note: This question is part of a series of questions that use the same or similar answer choices. An answer choice may be correct for more than one question in the series. Each question is independent of the other questions in this series. Information and details provided in a question apply only to that question.
You need to calculate a measure of central tendency and variability for the variables in a dataset that is grouped by using another categorical variable.
What should you use?

You have a slow Map Reduce job.
You need to optimize the job to control the number of mapper and runner tasks.
Which function should you use?

Note: This question is part of a series of questions that use the same or similar answer choices.
An answer choice may be correct for more than one question in the series.
Each question is independent of the other questions in this series.
Information and details provided in a question apply only to that question.
You need to calculate a measure of central tendency and variability for the variables in a dataset that is grouped by using another categorical variable.
What should you use?