The IZApplet is designed to be scripted with an analytic expression for current as a function of frequency, I( f), and phase as a function of frequency, Phase(f). It can be use to simulate an arbitrary AC circuit as a "black box." The script author must, of course, calculate the desired impedance function.
Example: What type of device is connected to the AC source? Use the slider to vary the frequency and then rest the mouse on the meter to read the values.