Introduction


gd is
a command-line oriented data plotting progam for computers running the UNIX or similar operating systems. The data can be 1- or 2-dimensional. The basic idea is that data to be plotted as well as layout instructions reside in a single text file in free format. These text files can be viewed by any file browser and edited by any text editor. In most cases only two commands (a read and a display) are sufficient to generate a graph of the data. Because many layout items are defaulted to "reasonable" values it should be rather easy to generate pictures without too many user interventions. Complex pictures can be built by overlaying new pictures on an already existing plot.
Data can be presented with various symbols, connecting lines, linewidths and colours. Text can be added at arbitrary positions in any size, direction and colour. Special symbols including math and greek characters are supported. Graphic elements like extra lines, arrows and other geometric figures may be added to a plot.
gd provides means to influence the layout of the picture (colours, linewidths, text sizes etc.) at various levels, either interactively, as a session default or in the data files.
A function fitting package is attached to allow least squares optimization of builtin and user defined functions.
gd supports command scripts so that complex pictures can be built by grouping several commands in a single script file which can readily be executed rather than typing individual commands.
Graphics output can be on any X-server for display or PostScript printers for paper copies. Encapsulated PostScript files can be used later in word processors like TeX
Historically gd is a derivative of the satangd program which once ran on GSI's MVS mainframe computer. Hence most legacy data and script files can be recycled. 
gd isn't
a free hand graphics program, a word processor or an image processing program, although a few features of such programs have been incorporated. For example, it is possible to add graphics elements to a picture, you can add text in formatting mode and there is some support to read and display bitmap files. However, for specific tasks you should rather use dedicated software like xfig, TeX or xview, respectively. 
Availability

gd is available for a variety of platforms
Versions for OS/2 and MacOSX are in preparation. At GSI, gd is installed on the central AIX and Linux computers. For use outside GSI an export package (tar'ed and compressed) is available on GSI's ftp server or here.
It comprises the executable, shell scripts, tutorial data and documentation in HTML and system specific format.