The program xrk is an interactive tool, based on the Motif widget set, for simulating systems of ordinary differential equations of the form
where is a vector valued function of (even) dimension less than or equal to eight, is a vector of parameters (dimension up to sixteen), and t is time.
The solutions of Eq. 1 are integrated in time via a fourth-order Runge-Kutta scheme. The solution curves for the different components are displayed pairwise in real time. (To describe what we mean by pairwise, suppose the dimension of the vector field is 2N. Then the xrk program displays N plot windows. The components and appear in the first plot window, the components and appear in the second plot window, and so on.)
The interface to the program allows one to easily do the following kinds of things.
The structure of the rest of this document is as follows. Section 2 describes the models that are included with the program. This is followed by a tutorial in Section 3 that uses some of these default models to demonstrate the main features of xrk. Section 4 provides a systematic discription of all of the program features and controls. Section 5 provides details of the formats of the various data files that the program can read or save. The last section describes some Maple programs that can be used to generate publication quality graphs from data produced by xrk.
Several conventions are used in this document to refer to program operations, window titles, Unix commands, file names, etc. Names of menu items, push button and text field labels, program names, file and directory names, and window titles are all set in typewriter text like this. All program operations that require a mouse action use the primary mouse button. For right handed users, this is the left mouse button, but this can be changed for left-handed users. To avoid confusion, the label ``MB1'' is used in this document to refer to the primary mouse button.
Unix commands meant to be issued in a terminal window are set on a line by themselves, in typewriter text, like the following command
xrk &The unix prompt is not shown.