Good apps, but two features suggested

[meijerhge]

I have tried this software and in my experience it works really well. I have taught courses on ODEs for years, and then used pplane. This new app is a good replacement as the code operates better, but some features of pplane are lacking. As an instructor I find the following two items would be helpful for students for the phase plane part.

1. Given an initial condition allow detection of periodic orbits (forward/backward in time), and then report the period too.
2. When defining the vector field one would preferably allow expressions/functions too. As an example, take the Morris-Lecar model with
   minf=(1+tanh((V-V1)/V2))/2
   taun=1/cosh((V-V3)/(2V4))
   ninf=(1+tanh((V-V3)/V4))/2
   V'=(-gCaminf*(V-ECa)-gKn(V-EK)-gL*(V-EL)+Iapp)/CM
   n'=phi*(ninf-n)/taun
   One could add all this into dV/dt and dn/dt, but, for readability, it is advantageous to be able to define these functions/expressions minf, ninf, taun. This example is about the functional form, I can provide numerical values if needed.