An Introduction to Statistical Learning Gareth James, Daniela Witten, Trevor Hastie and Robert Tibshirani

http://www-bcf.usc.edu/~gareth/ISL/index.html

Kindly discuss any of the following topics with additional references

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Chapter 10
10 Unsupervised Learning 373
10.1 The Challenge of Unsupervised Learning . . . . . . . . . . . 373
10.2 Principal Components Analysis . . . . . . . . . . . . . . . . 374
10.2.1 What Are Principal Components? . . . . . . . . . . 375
10.2.2 Another Interpretation of Principal Components . . 379
10.2.3 More on PCA . . . . . . . . . . . . . . . . . . . . . . 380
10.2.4 Other Uses for Principal Components . . . . . . . . 385
10.3 Clustering Methods . . . . . . . . . . . . . . . . . . . . . . . 385
10.3.1 K-Means Clustering . . . . . . . . . . . . . . . . . . 386
10.3.2 Hierarchical Clustering . . . . . . . . . . . . . . . . . 390
10.3.3 Practical Issues in Clustering . . . . . . . . . . . . . 399