R Package for Ecological Inference in 2x2 Tables CRAN Task View: Environmetrics (http://CRAN.R-project.org/view=Environmetrics) eco is a publicly available R package that implements the Bayesian and likelihood methods proposed in Imai, Lu, and Strauss (2008) for ecological inference in $2 \times 2$ tables as well as the method of bounds introduced by Duncan and Davis (1953). The package fits both parametric and nonparametric models using either the Expectation-Maximization algorithms (for likelihood models) or the Markov chain Monte Carlo algorithms (for Bayesian models). For all models, the individual-level data can be directly incorporated into the estimation whenever such data are available. Along with in-sample and out-of-sample predictions, the package also provides a functionality which allows one to quantify the effect of data aggregation on parameter estimation and hypothesis testing under the parametric likelihood models. Software Depends: R (>= 2.0), MASS Ying Lu <yl46@nyu.edu> Kosuke Imai <kimai@princeton.edu>, Ying Lu <yl46@nyu.edu>, Aaron Strauss <abstraus@Princeton.EDU>. GPL (>= 2) 2011-04-26 application/tgz http://CRAN.R-project.org/package=eco