Zelig is an easy-to-use, free, open source, general purpose statistics program for estimating, interpreting, and presenting results from any statistical method. Zelig turns the power of R, with thousands of open source packages — but with free ranging syntax, diverse examples, and documentation written for different audiences — into the same three commands and consistent documentation for every method. Zelig uses R code from many researchers, making it "everyone’s statistical software." We hope it becomes everyone’s statistical software for applications too, as we designed it so anyone can use it or add their methods to it. We aim for Zelig to be the best way to do analysis, prepare replication files, learn new methods, or teach.
Zelig includes many specific methods, based on likelihood, frequentist, Bayesian, robust Bayesian, nonparametric, and population and superpopulation theories of inference. Zelig adds considerable infrastructure to improve the use of existing methods. It translates hard-to-interpret coefficients into meaningful quantities of interest, along with the uncertainty estimates (generalizing Clarify for Stata); automates graphics and numerical summaries for all models; evaluates counterfactuals (incorporating WhatIf); combines multiply imputed data sets to impute missing data and correct for measurement error (via Amelia); automates bootstrapping for all models; allows for matching for causal inference to reduce model dependence (via MatchIt and cem); and generates replication data files (for Dataverse to satisfy community replication standards). Developers can make their R packages usable from Zelig by writing a few simple bridge functions. If you have suggestions improvements, we’d love to hear from you!