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 C++. Let's get started!

Let's say we have an array of integers denoting the ages of a group of people. We will demonstrate several basic aggregation methods using C++'s built-in functions:

Here's a brief overview of the above code snippet:

1. Number of people: Uses ages.size() to get the number of elements in the vector.
2. : Uses from the header to sum all elements in the vector.