Hierarchical clustering

Hierarchical clustering is like putting a lot of things into piles. Imagine you have a pile of multi-colored cubes (or whatever object of your choice). To put these cubes into piles, you can look at the colors and group the cubes with the same colors together. This is like hierarchical clustering - you group things that are similar together. This is done by creating a 'cluster' from each object and then combining the clusters that have the most in common. You can keep doing this until you have a few large clusters that each have objects that are very similar inside of them. So hierarchical clustering is a way of organizing a lot of things into groups by looking at what they have in common.