# Introduction

## Features at a glance

gretl is an econometrics package, including a shared library, a command-line client program and a graphical user interface.

User-friendly

  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.

Flexible

  You can choose your preferred point on the spectrum from interactive point-and-click to batch processing, and can easily combine these approaches.

Cross-platform

  gretl's home platform is Linux, but it is also available for MS Windows. I have compiled it on Mac OS X and AIX and it should work on any unix-like system that has the appropriate basic libraries (see ).

Open source

  The full source code for gretl is available to anyone who wants to critique it, patch it, or extend it. The author welcomes any bug reports.

Reasonably sophisticated

  gretl offers a full range of least-squares based estimators, including two-stage least squares and nonlinear least squares. It also offers (binomial) logit and probit estimation, and has a loop construct for running Monte Carlo analyses or iterative estimation of non-linear models. While it does not include all the estimators and tests that a professional econometrician might require, it supports the export of data to the formats of (GNU R) and (GNU Octave) for further analysis (see ).

Accurate

  gretl has been thoroughly tested on the NIST reference datasets. See .

Internet ready

  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.

International

  gretl will produce its output in English, French, Italian, Spanish or Polish, depending on your computer's native language setting.

## Acknowledgements

My primary debt is to Professor Ramu Ramanathan of the University of California, San Diego. A few years back he was kind enough to provide me with the source code for his program ESL (Econometrics Software Library), which I ported to Linux, and since then I have collaborated with him on updating and extending the program. For the gretl project I have made extensive changes to the original ESL code. New econometric functionality has been added, and the graphical interface is entirely new. Please note that Professor Ramanathan is not responsible for any bugs in gretl.

I am grateful to the authors of several econometrics textbooks for permission to package for gretl various datasets associated with their texts. This list currently includes William Greene, author of Econometric Analysis; Jeffrey Wooldridge (Introductory Econometrics: A Modern Approach); James Stock and Mark Watson (Introduction to Econometrics); Damodar Gujarati (Basic Econometrics); and Russell Davidson and James MacKinnon (Econometric Theory and Methods).

GARCH estimation in gretl is based on code deposited in the archive of the Journal of Applied Econometrics by Professors Fiorentini, Calzolari and Panattoni, and the code to generate p-values for Dickey Fuller tests is due to James MacKinnon. In each case I am grateful to the authors for permission to use their work.

With regard to the internationalization of gretl, I wish to thank Ignacio Díaz-Emparanza, Michel Robitaille, Cristian Rigamonti and Tadeusz Kufel, who prepared the Spanish, French, Italian and Polish translations respectively.

I have benefitted greatly from the work of numerous developers of open-source software: for specifics please see to this manual. My thanks are due to Richard Stallman of the Free Software Foundation, for his support of free software in general and for agreeing to adopt gretl as a GNU program in particular.

Many users of 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 and Dirk Eddelbuettel, who maintains the gretl package for Debian GNU/Linux. Besides making good suggestions, Riccardo Jack Lucchetti has contributed substantial code and econometric expertise.

## Installing the programs

### Linux

On the Linux Terminology is a bit of a problem here, but in this manual I will 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 gretl code yourself or making use of a pre-built package. Ready-to-run packages are available in rpm format (suitable for Red Hat Linux and related systems) and also deb format (Debian GNU/Linux). I am grateful to Dirk Eddelbüttel for making the latter. If you prefer to compile your own (or are using a unix system for which pre-built packages are not available) here is what to do.

1. Download the latest gretl source package from gretl.sourceforge.net.

2. Unzip and untar the package. On a system with the GNU utilities available, the command would be `tar -xvfz gretl-N.tar.gz` (replace `N` with the specific version number of the file you downloaded at step 1).

3. Change directory to the gretl source directory created at step 2 (e.g. `gretl-1.1.5`).

4. The basic routine is then

       	      ./configure
       	      make
       	      make check
       	      make install

   However, you should probably read the `INSTALL` file first, and/or do `./configure --help` first to see what options are available. One option you way wish to tweak is `--prefix`. By default the installation goes under `/usr/local` but you can change this. For example `./configure --prefix=/usr` will put everything under the `/usr` tree. In the event that a required library is not found on your system, so that the configure process fails, please take a look at of this manual.

As of version 0.97 gretl offers support for the gnome desktop. To take advantage of this you should compile the program yourself (as described above). If you want to suppress the gnome-specific features you can pass the option `--without-gnome` to `configure`.

### MS Windows

The MS Windows version comes as a self-extracting executable. Installation is just a matter of downloading `gretl_install.exe` and running this program. You will be prompted for a location to install the package (the default is `c:\userdata\gretl`).

### Updating

If your computer is connected to the Internet, then on start-up 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 gretl's File, Preferences, General menu.

The MS Windows version of the program goes a step further: it tells you that you can update gretl automatically if you wish. To do this, follow the instructions in the popup window: close gretl then run the program titled gretl updater (you should find this along with the main gretl program item, under the Programs heading in the Windows Start menu). Once the updater has completed its work you may restart gretl.