AI-016: 吴恩达教授（Andrew Ng）的机器学习课程学习笔记55.Clustering

本文是学习Andrew Ng的机器学习系列教程的学习笔记。教学视频地址：

https://study.163.com/course/introduction.htm?courseId=1004570029#/courseDetail?tab=1

55. Clustering

Unsupervised learning

K Means Algorithm is the most popular and the most widely used one by far.

Find cluster center

Step to use K-Means:

Optimization objective

to avoid local optima, just try multiple, random initializations:

choosing the number of clusters:

by far the most common way of choosing the number of clusters, is still choosing it manually by looking at visualizations or by looking at the output of the clustering algorithm or something else.

elbow method 肘关节方法 choose the elbow of above figure.:

for the later downstream purpose ：