# Unsupervised Learning

Unsupervised Learning!

## Principle components analysis

## Clustering

K-means Clustering

```
Algorithm:
1. Assign data points to a group
2. Iterate through until no change:
1. Find centroid
2. Find the point that is closest to the centroids. Assign that data point to the corresponding group of the centroids.
.. admonition:: How Many Groups
:class: warning
The art of chosing K.
Hierarchical Clustering
```

Bottom-up hierarchical groups can be read out from dendrogram.