Welcome to today's lesson! Our topic for the day is data aggregation, a crucial aspect of data analysis. Like summarizing a massive book into key points, data aggregation summarizes large amounts of data into important highlights.

By the end of today, you'll be equipped with several aggregation methods to summarize data streams in Kotlin. Let's get started!

Let's say we have a list of numbers denoting the ages of a group of people:

Common questions we might ask: How many people are in the group? What's their total age? Who's the youngest and the oldest? Kotlin's handy built-in functions size, sum, minOrNull, and maxOrNull have our answers:

• size: This function returns the number of elements in the list, helping us determine how many people are in the group.
• : It calculates the total of all elements in the list, representing the combined age of all individuals.