Introduction We’ve been writing on the distribution density shapes expected for probability models in ROC (receiver operator characteristic) plots, double density plots, and normal/logit-normal densities frameworks. I thought I would re-approach the issue with a specific family of examples. Definitions Let’s define a “probability model” as a ...

The double density plot contains a lot of useful information. This is a plot that shows the distribution of a continuous model score, conditioned on the binary categorical outcome to be predicted. As with most density plots: the y-axis is an abstract quantity called density picked such that the area […]

This note is a little break from our model homotopy series. I have a neat example where one combines two classifiers to get a better classifier using a method I am calling “ROC surgery.” In ROC surgery we look at multiple ROC plots and decide we want to cut out […]

So are model homotopies commonly used? Yes, they are. As an example consider glmnet: Jerome Friedman, Trevor Hastie, Robert Tibshirani (2010). Regularization Paths for Generalized Linear Models via Coordinate Descent. Journal of Statistical Software, 33(1), 1-22. URL http://www.jstatsoft.org/v33/i01/. From help(glmnet): library(glmnet) x = matrix(rnorm(100 * 20), 100, 20) g2 = […]

Nina Zumel just completed an excellent short sequence of articles on picking optimal utility thresholds to convert a continuous model score for a classification problem into a deployable classification rule. Squeezing the Most Utility from Your Models Estimating Uncertainty of Utility Curves This is very compatible with our advice to […]