ELI5: knn regression

What is KNN regression?

Imagine you want to guess how much a house costs, but you don't know the formula. Instead, you find the 5 houses closest to it (by size, location, etc.) and guess that your house costs about the same as the average of those 5 houses [1]. That's basically KNN regression — it makes predictions by looking at the nearest neighbors [1].

Why does it work?

The idea is that things that are similar to each other tend to behave similarly. If your new house is in the same neighborhood as 5 other houses, those houses probably tell you a lot about what your house should cost [1][2].

What does it need to work?

You need to pick a number called K, which is how many nearby points to look at (like deciding to look at 3 neighbors, 5 neighbors, or 10 neighbors) [4]. You also need to measure distance — figuring out what "close" means, usually by comparing features like size or location [1].

How do you use it?

Once you have your K number and a distance measure, the algorithm finds the K closest data points to your new point, takes their average values, and that average becomes your prediction [1][3].