# An activator-inhibitor system   ch4-activator-inhibitor.ode 
# See Chapter 4.4.2 (Nullclines and Trapping Regions) in our textbook.
dx/dt = (sigma/(1+y))*x^2/(1+x^2/kappa^2)-x
dy/dt = rho*(x^2/(1+x^2/kappa^2)-y)

# Set the default values of the parameters:
# Don't put spaces between the parameter name, the equal sign, and the parameter value!
par sigma=4.0,rho=0.5,kappa=1

# Set the default initial conditions:
init x=1.0  y=0.5

# Set the default axes for a phase plane plot of y versus x: 
@ xplot=x, yplot=y

# Set the default stopping time and time step
@ total=20, dt=0.01

# Set the default viewing window
@ xlo=0.0,xhi=2.5,ylo=0.0,yhi=1.5
done