# Chapter 3 Summarising data

“The Answer to the Great Question … Of Life, the Universe and Everything … Is … Forty-two,” said Deep Thought, with infinite majesty and calm.
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In this chapter you will find out how to:

• summarise data using: group_by(), summarise(), and mutate();
• reshape data between the wide and long formats: pivot_wider() and pivot_longer();
• select() columns and arrange() (sort) rows.

The exercises at the end of this chapter combine all of the above to give context and show you more worked examples.