I made this little function plotter app to help me with some research i was doing at the university. It can be used as an app, which can plot two arbitrary functions simultaneously, each with 3 adjustable variables.
The technical part if you're interested(AKA what is a Hodgkin-Huxley equation?):
It plots for me Hodgkin-Huxley activation and inactivation curves. A little explanation: The Hodgkin-Huxley formalism is a way to describe how neurons transmit signals. Neurons transmit signals by electric impulses. There is always a voltage difference between the interior and the exterior of the cell(called membrane potential). If i change this potential somewhere, this temporary change will spread across the cell's surface, like a wave. The mechanisms responsible for this process are molecules in the cell membrane(called ion channels), which can open to let ions flow trough, which causes change in the membrane potential. There are tons of different ion channels, but most of them can be described with the Hodgkin-Huxley formalism. These curves describe how much will be these channels open ( 0-closed; 1-fully open) at different membrane potential values. To make things more complicated each ion channel is modeled by 2 curves (activation and inactivation) and the product at a current membrane potential value will be the actual channel activity. Note, that this is a really simplified description (for example these channels have time-dependence too), if you want to really understand the concept i recommend reading on Wikipedia or Scholaropedia about this topic.