\chapter{Introduction} \label{intro} \section{Features at a glance} \label{features} \app{Gretl} is an econometrics package, including a shared library, a command-line client program and a graphical user interface. \begin{description} \item[User-friendly] \app{Gretl} offers an intuitive user interface; it is very easy to get up and running with econometric analysis. Thanks to its association with the econometrics textbooks by Ramu Ramanathan, Jeffrey Wooldridge, and James Stock and Mark Watson, the package offers many practice data files and command scripts. These are well annotated and accessible. Two other useful resources for gretl users are the available documentation and the \href{http://gretl.sourceforge.net/lists.html}{gretl-users} mailing list. \item[Flexible] You can choose your preferred point on the spectrum from interactive point-and-click to batch processing, and can easily combine these approaches. \item[Cross-platform] \app{Gretl}'s ``home'' platform is Linux but it is also available for MS Windows and Mac OS X, and should work on any unix-like system that has the appropriate basic libraries (see Appendix~\ref{app-build}). \item[Open source] The full source code for \app{gretl} is available to anyone who wants to critique it, patch it, or extend it. See Appendix~\ref{app-build}. \item[Sophisticated] \app{Gretl} offers a full range of least-squares based estimators, either for single equations and for systems, including vector autoregressions and vector error correction models. Several specific maximum likelihood estimators (e.g.\ probit, ARIMA, GARCH) are also provided natively; more advanced estimation methods can be implemented by the user via generic maximum likelihood or nonlinear GMM. \item[Extensible] Users can enhance \app{gretl} by writing their own functions and procedures in \app{gretl}'s scripting language, which includes a reasonably wide range of matrix functions. \item[Accurate] \app{Gretl} has been thoroughly tested on several benchmarks, among which the NIST reference datasets. See Appendix~\ref{app-accuracy}. \item[Internet ready] \app{Gretl} can access and fetch databases from a server at Wake Forest University. The MS Windows version comes with an updater program which will detect when a new version is available and offer the option of auto-updating. \item[International] \app{Gretl} will produce its output in English, French, Italian, Spanish, Polish, Portuguese, German or Basque, depending on your computer's native language setting. \end{description} \section{Acknowledgements} \label{ack} The \app{gretl} code base originally derived from the program \app{ESL} (``Econometrics Software Library''), written by Professor Ramu Ramanathan of the University of California, San Diego. We are much in debt to Professor Ramanathan for making this code available under the GNU General Public Licence and for helping to steer \app{gretl}'s early development. We are also grateful to the authors of several econometrics textbooks for permission to package for \app{gretl} various datasets associated with their texts. This list currently includes William Greene, author of \emph{Econometric Analysis}; Jeffrey Wooldridge (\emph{Introductory Econometrics: A Modern Approach}); James Stock and Mark Watson (\emph{Introduction to Econometrics}); Damodar Gujarati (\emph{Basic Econometrics}); Russell Davidson and James MacKinnon (\emph{Econometric Theory and Methods}); and Marno Verbeek (\emph{A Guide to Modern Econometrics}). GARCH estimation in \app{gretl} is based on code deposited in the archive of the \emph{Journal of Applied Econometrics} by Professors Fiorentini, Calzolari and Panattoni, and the code to generate \emph{p}-values for Dickey--Fuller tests is due to James MacKinnon. In each case we are grateful to the authors for permission to use their work. With regard to the internationalization of \app{gretl}, thanks go to Ignacio Díaz-Emparanza (Spanish), Michel Robitaille and Florent Bresson (French) , Cristian Rigamonti (Italian), Tadeusz Kufel and Pawel Kufel (Polish), Markus Hahn and Sven Schreiber (German), Hélio Guilherme (Portuguese) and Susan Orbe (Basque). \app{Gretl} has benefitted greatly from the work of numerous developers of free, open-source software: for specifics please see Appendix~\ref{app-build}. Our thanks are due to Richard Stallman of the Free Software Foundation, for his support of free software in general and for agreeing to ``adopt'' \app{gretl} as a GNU program in particular. Many users of \app{gretl} have submitted useful suggestions and bug reports. In this connection particular thanks are due to Ignacio Díaz-Emparanza, Tadeusz Kufel, Pawel Kufel, Alan Isaac, Cri Rigamonti, Sven Schreiber, Talha Yalta, Andreas Rosenblad, and Dirk Eddelbuettel, who maintains the \app{gretl} package for Debian GNU/Linux. \section{Installing the programs} \label{install} \subsection{Linux} \label{linux-install} On the Linux\footnote{In this manual we use ``Linux'' as shorthand to refer to the GNU/Linux operating system. What is said herein about Linux mostly applies to other unix-type systems too, though some local modifications may be needed.} platform you have the choice of compiling the \app{gretl} code yourself or making use of a pre-built package. Building \app{gretl} from the source is necessary if you want to access the development version or customize \app{gretl} to your needs, but this takes quite a few skills; most users will want to go for a pre-built package. Some Linux distributions feature \app{gretl} as part of their standard offering: Debian, for example, or Ubuntu (in the \emph{universe} repository). If this is the case, all you need to do is install \app{gretl} through your package manager of choice (e.g.\ \app{synaptic}). Ready-to-run packages are available in \app{rpm} format (suitable for Red Hat Linux and related systems) on the \app{gretl} webpage \url{http://gretl.sourceforge.net}. However, we're hopeful that some users with coding skills may consider \app{gretl} sufficiently interesting to be worth improving and extending. The documentation of the libgretl API is by no means complete, but you can find some details by following the link ``Libgretl API docs'' on the \app{gretl} homepage. People interested in the \app{gretl} development are welcome to subscribe to the \href{http://gretl.sourceforge.net/lists.html}{gretl-devel} mailing list. If you prefer to compile your own (or are using a unix system for which pre-built packages are not available), instructions on building \app{gretl} can be found in Appendix~\ref{app-build}. \subsection{MS Windows} \label{windows-install} The MS Windows version comes as a self-extracting executable. Installation is just a matter of downloading \verb+gretl_install.exe+ and running this program. You will be prompted for a location to install the package. \subsection{Updating} \label{updating} If your computer is connected to the Internet, then on start-up \app{gretl} can query its home website at Wake Forest University to see if any program updates are available; if so, a window will open up informing you of that fact. If you want to activate this feature, check the box marked ``Tell me about gretl updates'' under \app{gretl}'s ``Tools, Preferences, General'' menu. The MS Windows version of the program goes a step further: it tells you that you can update \app{gretl} automatically if you wish. To do this, follow the instructions in the popup window: close \app{gretl} then run the program titled ``gretl updater'' (you should find this along with the main \app{gretl} program item, under the Programs heading in the Windows Start menu). Once the updater has completed its work you may restart \app{gretl}. %%% Local Variables: %%% mode: latex %%% TeX-master: "gretl-guide" %%% End: