The Gwx Story / Clopper Almon

There are hundreds, maybe thousands, of books about how to use some specific computer program, but there are few if any books about how a program was written, about what was in the mind of the designer and programmer as the project evolved and took form, as problems emerged and were solved. Yet this process of program development is one of the important human activities in today's world. It needs to be brought out of the shadows of the programmer's magical, alchemical laboratory. Examples of program development need to be openly available for study. Such description is particularly important for programs that are intended to be open-source and perhaps further developed and maintained by people who never even knew the original creator.

Gwx is such a program. It is written in C++ and uses wxWidgets for creating a cross-platform graphical user interface (GUI). Some familiarity with C++ or at least C is assumed, but the use of wxWidgets is explained from the beginning.

This explanation is perhaps one of the most important features of the book, for the necessity to write for a GUI has greatly complicated the life of the programmer, and there are few extended accounts of how it is done. Fortran and C had a couple of dozen techniques the programmer needed to know; C++ added a few more. But Gui programming may require another hundred or more, each with many details. It is far too much to remember. The use of a helper program such as wxSmith in the Code::Blocks development environment becomes necessary. This book serves also as an extensive tutorial in the application of this tool.

Gwx is a regression and economic model-building program designed to be used with the author's book The Craft of Economic Modelling, available at www.inforum.umd.edu. It is his conviction that the best way to gain an understanding of how the macro economy works is to try to build an econometric model of it. Gwx is intended to help make that experience readily available. It is a successor to G7, developed by the author and associates in the Inforum group within the Economics department at the University of Maryland. Although G7 is freely available from the Inforum website, it is limited to the Windows operating system and is not open-source. Gwx and this book are written with the hope that users of Gwx who know some C++ will want to look at the code and understand what is going on “under the hood.”

At present, August of 2016, Gwx is developed to the point that it should be useful for building macroeconomic models. It does not yet have the features that make G7 ideal for building multisectoral models. Present capacities include assigning data banks, reading in data, creating new data series by algebraic formulas, logarithm and exponential functions, the @cum function for creating stocks from flows, the @atoq and @atoqi functions for creating quarterly series from annual series, and the @mtoq() function for making a quarterly series from a monthly one. It does ordinary least-squares regression, regression with “soft” linear constraints on the regression coefficients and “sma” regression to softly impose polynomial constraints on coefficients of a distributed lag. Results are saved in files which can potentially be used to build models or write papers. It draws graphs with carefully labeled axes and a legend, as well as a title and subtitle. Graphs are saved in the industry standard png format.

Open the book and step into the workshop of the developer-magician!