The Zelig core team is pleased to announce the alpha release of Zelig 4.

Designated as the "Developer Update", Zelig 4 offers a wide-range of improvements to ease the process of adding new statistical models to the already extensive Zelig software suite. Significantly, this release is packaged with a brand-new API, geared towards reducing the complexity and length of Zelig's development functions - the zelig2, param and qi methods. In addition to this, Zelig now brandishes a package-creator (zelig.skeleton) that operates in the same vein as R's core function "package.skeleton".

In addition to changes in the development toolkit, Zelig has now been split across 13 distinct packages. This change has been made to refine the scope of Zelig and its add-ons. In particular, this restructuring of Zelig into a full software suite allows developers to contribute, develop and repair add-on packages without tinkering with the Zelig API and core functionality. 

While this release's prime focus has been improving the developer toolkit and restructuring the software suite, Zelig 4 offers an end-user experience completely identical to previous versions. That is, zelig's basic functions - zelig, setx and sim - ostensibly remain unchanged in functionality for available statistical models.

For full details concerning changes between Zelig 3.5 and Zelig 4, please refer to:
 http://zeligdev.github.com/


New Features
------------

Some of the new available features are:

A revised developer API. The primary developer methods - zelig2, param and sim - have been reimplemented to use a sleeker, simpler API. For information, please read the Zelig developer's manual found here:
  http://zeligdev.github.com/files/booklet.pdf

The core package has been restructured and minimized. In particular, Zelig core now contains only code essential to its operation, while all non-essential tasks have been made into specific R-packages. For a complete list of official Zelig packages, please refer to:
  https://github.com/zeligdev

Development tools for contributors have been added to the core package. In particular, the "zelig.skeleton" function is packaged within Zelig-core in order to facilitate the rapid development of new Zelig packages.

The Zelig software suite has grown to include a total of 7 R-packages. This change offers a simple and easy method for ensuring that development and bug-fixing within any particular Zelig add-on will leave the remainder of the Zelig software suite unchanged.

A hook API has been integrated into the core package, in order to reduce the necessity to directly alter the zelig, setx and sim methods.

Roxygen-compliant documentation has become standard in all Zelig packages. This offers an easy way to manage Rd documentation, dependencies and exports from within the R code itself. That is, documentation is more tightly paired with the actual R code. For more information about Roxygen, please refer to:
  http://roxygen.org/


GitHub
------

Zelig is now on GitHub! Fork an add-on package or contribute bug-finds today!

For a full listing of official packages and their repositories, please see:
 https://github.com/zeligdev


Links
-----

The following comprises a list of relevant information for Zelig 4:
 * Website: http://zeligdev.github.com/
 * Package Repositories: https://github.com/zeligdev/
 * Installation Guide: http://zeligdev.github.com/files/zelig.pdf
 * Zelig Manual: http://zeligdev.github.com/#install
 * Available and Missing Add-on Packages: http://zeligdev.github.com/#models


Questions
---------

For any particular questions on developing new Zelig models, please send all mail to:
  zelig@lists.gking.harvard.edu


Zelig v4.0-4 Release Notes (May 16, 2011)


Introduction
================================================================================
This document is a brief overview of the current state of the Zelig project as
of the 4.0-3 release. This release hopes to maintain the canonical Zelig syntax
and interface for end-users, while supplying developers with tools to aid in
the development of effective statistical modeling techniques. Emphasis has been
placed on readability and modularity.

As a result of this gargantuan change, a plethora of features, API
functionality, and documentation has been added to the Zelig R-package. Several
previously existing models, however, have been removed temporarily or moved
from the Zelig core package to more-specific Zelig extensions.


Project Information
================================================================================
The Zelig software suite is an easy-to-use R-package geared towards making
complex statistical techniques available to end users, particularly those
researching the quantitative social sciences. In particular, it offers unifying
syntax and programming-style between seemingly disparate and unrelated 
statistical mdoels.

To facilitate this purpose, Zelig (as of May 16th, 2011) includes an array of
programming tools, geared towards allowing the rapid development, debugging, 
and inclusion of new statistical models. That is, Zelig now facilitates and
encourages collaboration between novel and pre-existing statistical packages.


Author Information
================================================================================
Zelig is a collaborative effort by Harvard's Institute for Quantitive Social
Sciences (Harvard IQSS). Publications, software releases, and additional
information can be found at:
  http://gking.harvard.edu/
  http://iq.harvard.edu/


Licensing
================================================================================
Zelig is licensed under the GNU General Public License version 2, and as such
can be freely used and edited given proper attribution to Harvard's IQSS
Department.


What's New in this Release?
================================================================================
This release offers a large variety of coding style changes, as well as core
functionality. Please carefully read the following:

Major Changes (from version 3.5)
--------------------------------------------------------------------------------
- Models are now added to Zelig as separate extensions. The method
  'zelig.skeleton' has been added to the R-package to facilitate this change.
- The main Zelig package now contains a mere 8 models. 22 additional models are
  available via extensions, geared towards adding specific functionality to the
  Zelig software suite.
- zelig.skeleton: a method used to create blank zelig packages. This follows
  the style and format of the R-core method 'package.skeleton'
- Simplified zelig2-function API. See "?zelig2" within an R-session for help
- Enhanced API for 'param' and 'qi' functions. See develoepr documentation for
  more information

Minor Changes (from version 3.5)
--------------------------------------------------------------------------------
- Slight changes to the plotting of simulated quantities of interest. Most
  changes are stylistic
- Quantities of interest using two different sets of explanatory variables now
  output information containing concerning the simulations of the second 'setx'
  object's Predicted Values and Expected Values. This was previuosly not the
  case
- ZeligListModels: a method used to list available models, installed on the
  current operating system.
- More robust support for various ways of describing 'terms' of a statistical
  model. This is essentially light error-detection

Missing Features
--------------------------------------------------------------------------------
- The 'setx' method currently doesn not support setting multiple
  counterfactuals in a single call to 'setx'. This feature is under current
  development, and should soon be admitted into the main branch.
- "ternaryplot" plotting style is ommitted from the core package, and will be 
  instead moved to the 'bivariate' and 'multinomial' Zelig modules.
- "Average Treatment Effect" quantities of interest are not being included in 
  zelig models temporarily. Simulation of these qi's will return pending a 
  minor update to the 'setx' function.
