help

- SVD
	- ROC curve
	- median of TPs and TNs
- PCA
	- RandomizedPCA
	- IncrementalPCA
	- Mean-centering
	- Scaling
	- http://metaoptimize.com/qa/questions/8076/does-not-centering-data-hurt-when-doing-pca
	- http://www.quora.com/Does-scikit-learn-have-a-PCA-implementation-for-sparse-matrices
	- http://docs.scipy.org/doc/scipy/reference/generated/scipy.sparse.linalg.svds.html#scipy.sparse.linalg.svds
	- http://stackoverflow.com/questions/10718455/apply-pca-on-very-large-sparse-matrix
	- http://stats.stackexchange.com/questions/134282/relationship-between-svd-and-pca-how-to-use-svd-to-perform-pca
	- http://stats.stackexchange.com/questions/94103/pca-on-non-centered-data
	- http://stats.stackexchange.com/questions/36254/mean-centering-for-pca-in-a-2d-array-across-rows-or-cols
- SFAM
- EM
	- how?
- LDA
	- http://stackoverflow.com/questions/10718455/apply-pca-on-very-large-sparse-matrix
	- https://pypi.python.org/pypi/lda