Simulink is of course the modern replacement for an analog computer and does a lot more. For open source there is Scilab xcos and underneath it OpenModelica.

Simulink is of course the modern replacement for an analog computer and does a lot more. For open source there is Scilab xcos and underneath it OpenModelica. It would be crude and inefficient but you also could use spice and rig up op amps just like a physical analog computer if you just want to learn or if spice is your comfort zone. Or if you want to add additional analog circuitry or spice models. It’s the 21st century so it will be fast enough computationally for small to medium sized models.