Jul 24, 2013 — Non-Negative Matrix Factorization — Non-negative matrix factorization (nnmf) is an unsupervised machine learning method for (you predicted it, strictly positive) data!  The goal of nnmf, of course, is dimensionality reduction.  We start with a dataset, X (size N x p), and want to decompose... Read more

Jul 24, 2013 — Sparse K-Means Clustering "Sparcl" — Tibshirani and Witten introduced a variation of K-Means clustering called “Sparcl.”  What gives it this name?  It is a method of sparse clustering that clusters with an adaptively chosen set of features, by way of the lasso penalty.  This method... Read more

Jul 21, 2013 — Why have clinical decision support systems (CDSS) not worked? — This is by no means an all encompassing list, but I wanted to have a place to jot down some ideas for why CDSS are largely just mediocre.  The big picture summary is that there are problems with the models... Read more

Jul 21, 2013 — The Arden Syntax — What is the Arden Syntax? “A standard for representing clinical and scientific knowledge in an executable format.”* The goal of the Arden Syntax is to be a standard programming language for the implementation of clinical decision support systems. It gets... Read more