I am using XPP to analyse the phase plots of my two variable (c and n) systems. Besides the two dynamic variables I have another static variable F which depends on one of the parameters, say A, such that F is a function of parameter A. Now I have written the equation of F as a derived parameter (because it depends solely on the parameters).

I need to use the log sigmoidal function in the equation of F, but xpp doesnt accept that! It accepts sin, cos, etc functions mentioned in the manual provided online but not log sigmoid. I am declaring it as logsig(A) similar to as we do in MATLAB but it doesn't seem to work.

I would be extremely elated if somebody could help me in this regard...

(I hope my question is clear. I've been stuck on it for a long time so any help would be highly appreciable!! :-) )