Political Science Computational Laboratory


pscl is an R package providing classes, methods and test data for

Historical note

The Political Science Computational Laboratory was the name of Simon Jackman’s research group at Stanford University’s Department of Political Science (2002-2014), where this package was first developed.

The hurdle and count data models were extensively re-written and updated by Achim Zeileis and Christian Kleiber.


Most users should use latest stable release of the package, which can be installed from CRAN by running


The development version can be installed directly from GitHub by running

install.packages("devtools") ## if not already installed