The Machine Learning “Advent Calendar” Day 4: k-Means in Excel

K-means is an unsupervised machine learning algorithm used to create meaningful labels by grouping data points into clusters based on proximity. The process, known as Lloyd's algorithm, iteratively assigns each point to the nearest centroid and then recalculates the centroids as the average of the points in each new cluster until convergence. This tutorial demonstrates how to implement the algorithm from scratch in Excel, starting with a simple 1D example and moving to a 2D case. It also explains the Elbow Method, a technique for finding the optimal number of clusters (k) by plotting the inertia for different k values to find the point of diminishing returns.