ELI5: Explain Like I'm 5

Piecewise regression

Okay, so imagine you are playing with your toys and you have a bunch of blocks in different shapes and sizes. Your blocks have different colors and you want to group them by color. So you start with the blue blocks and put them all in a pile. Then you do the same with the red blocks and the green blocks.

Piecewise regression is similar to what you did with your blocks. It is a way to group or separate data points (like the blocks) into different groups based on certain conditions or rules. But, instead of grouping by color, in piecewise regression, we group data points by the values of a certain variable, like time or position.

Here's an example: imagine you are trying to measure the temperature of a room over a whole day. You take temperature readings every hour and write them down. When you look at the numbers, you notice that the temperature changes throughout the day, going up and down. It's not a straight line, it's a curve. But it's not just any curve, it has different parts with different slopes (the angle of the curve).

Now, imagine that you want to find a way to show how the temperature changes over time in a graph. You could draw a line that fits all the data points, but that wouldn't be accurate because the temperature changes at different rates throughout the day. That's where piecewise regression comes in.

Piecewise regression allows you to separate the data into groups based on different conditions. In our temperature example, you could group the data points into two different time periods, say "morning" and "afternoon". Then, you could fit a line to each group separately, creating two different lines in your graph. This way, you can see how the temperature changes at different rates during the morning and afternoon.

In summary, piecewise regression is like sorting your toys or grouping your data points into different groups based on certain conditions. This helps you to see patterns and trends that you might not have noticed if you had just looked at all the data points together.