# ecological model
f=x*y/(1+alpha*x)
x'=x*(1-beta*x)-f
y'=y*(-gamma-delta*y)+f
par alpha=.3,beta=.01,gamma=1,delta=.5
@ bound=500,xp=x,yp=y,xlo=0,ylo=0,xhi=100,yhi=10
@ nmesh=100
done