An unsupervised algorithm that finds k group centers. Repeat: assign each point to its nearest centroid → move each centroid to the mean of its members → repeat until nothing moves.
Iteration0
PhaseInitial
Inertia (total within-SS)—
3
Caveats: k-means assumes round clusters of similar size, and the result depends on the random starting centroids — try "New centroids" a few times to see different solutions. Choosing k is its own problem (look up the elbow method).