Can the computer find hidden groups?

The Case. Here are the sizes and weights of some animals, all jumbled together with no labels at all. Can a computer sort them into sensible groups on its own? This is how streaming apps quietly group listeners with similar taste, or shops cluster their customers — no answer key needed.

Your tools. scikit-learn's KMeans is unsupervised learning: it finds patterns with no answer key.

Investigate. Press Run. The colours are the groups the computer discovered; the red X's mark the centre of each group.

• Change n_clusters to 3 — does it invent a third group?
• This is how apps group customers or songs without being told the categories.