How can I control a pen plotter DIRECTLY with a joystick or touchpad?

Hello,
I'd like to connect a joystick to a pen plotter, and (with "draw" straight from my joystick in real time (without having to save a file and pressing "plot").

Can someone point me to an existing setup like this, or suggest a known solution?

Thanks!

What is the input to the plotter, serial, analog, HPGL,...?