# van der Pol equation ch1-van-der-Pol.ode 
# First, write the 2nd-order van der Pol equation as a system
# of two first-order ODEs as follows:
dx/dt = y
dy/dt = -beta*(x^2-1)*y - x

# Set the default value of the parameter beta:
# Don't put spaces between the parameter name, the equal sign, and the parameter value!
par beta=1.0

# Set the default initial conditions:
init x=1.0  y=0.0

# Set the axes to plot a trajectory in the phase plane: 
@ xplot=x, yplot=y

# Set the stopping time, time step, and default viewing window
@ total=10,dt=.01,xlo=-3.0,xhi=3.0,ylo=-3.0,yhi=3.0
done