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1. Overview

Grace (formerly Xmgr) is a popular plotting program for Unix that features a GUI for WYSIWYG generation of publication quality 2-D graphs. The grace-module provides a high-level interface between the S-lang interpreter and the Grace plotting application, permitting the creation of multiple Grace instances and allowing an arbitrary number of Grace windows to be open.

The module was developed and tested with Grace-5.1.20, using Debian ``Etch'' as the underlying OS. As the module makes extensive use of qualifiers, it will not work for versions of S-lang prior to 2.1. It is also unlikely to work with newer development versions of Grace (grace-6) because the mechanism used for communicating with Grace-5 appears to be unsupported in Grace-6. The module interacts with Grace via a one-way pipe that feeds it commands using the approach recommended in the Grace User's Guide. As this pipe is one-way, it is impossible for the module to query Grace about its plotting state. For this reason, the module tries to maintain enough state to avoid potential conflicts with Grace. For example, the module will not instruct Grace to switch to a log scale without first making sure that no negative values have been plotted. If negative values were plotted, the module will first change the world-coordinate system to values that are appropriate for log plots.

The development for this release has been focused towards the types of 2-D graphs that are common in the physical sciences--- specifically, Cartesian (X,Y) plots with various combinations of error-bars. While the module can be used to produce pie and bar charts, no work has been done to facilitate the construction of such graphs. A future version of the module will address these shortcomings.


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