BAT  0.9.4
The Bayesian analysis toolkit
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BAT Documentation

The Bayesian Analysis Toolkit is a software analysis package which allows to address the main goals of a typical data analysis:

  • compare model predictions with data,
  • draw conclusions on the validity of the model as a representation of the data and
  • extract the possible values of parameters within the context of a model.

The BAT is based on Bayes' Theorem and is realized with the use of Markov Chain Monte Carlo. This gives access to the full posterior probability distribution and enables straightforward parameter estimation, limit setting and uncertainty propagation.

The BAT is implemented in C++ on top of CERN's ROOT with emphasis put on flexibility and modularity in defining models while keeping in mind the reliability and speed requirements of the numerical operations.

The information about the main features introduced in this version can be found in doc/ The detailed list of changes can be found in doc/ChangeLog.


See doc/CREDITS file for list of contributors to BAT.


All BAT releases are available from The source code is managed online at BAT is open-source software under the GPLv3 or later. See doc/COPYING and doc/LICENSE for licensing details.


Directory bat/:

  • doc/: documentation about BAT
  • examples/: well commented example programs
  • BAT/: BAT header files
  • src/: BAT source files
  • models: models and interfaces for BAT
  • tools: tools useful for BAT
  • instructions to install BAT on your system
  • basic information about BAT

Other files distributed with BAT are part of installation and configuration system.


See the file for installation instructions. The instructions for the latest development version are also available "online".


For additional information and contacting the authors, please consult the BAT web page at If you want to report an error or file a request, please file an issue at