Determining the Number of Clusters
===== Recommended Reading =====
* [[https://statweb.stanford.edu/~gwalther/gap|Estimating the number of clusters in a dataset via the gap statistic]] by Tibshirani et al. (2001)
* [[http://statweb.stanford.edu/~gwalther/predictionstrength.pdf|Cluster Validation by Prediction Strength|]] by Robert Tibshirani and Guenther Walther (2005)