## Handling auxiliary functions in the construction of the odefile

If complicated expressions arise several times in the definition of a dynamical system then is often useful to give them a name. A simple example is the following system (a catalytic oscillator, (60):

|  |  | (31)

where . When `SysGUI.new` is used to create the odefile of the system then is not necessary to ``expand" the auxiliary function for The system can be introduced as

    z=1-x-y-s
    x'=2*q1*z^2-2*q5*x^2-q3*x*y
    y'=q2*z-q6*y-q3*x*y
    z'=q4*z-k*q4*s

We note that the definition of the auxiliary functions must precede the definiton of the right hand sides.

The corresponding odefile is `cataloscill.m` in the directory `Testruns/TestSystems.`