chaintest - a three-species food chain model

Calling Sequence

chaintest([f_l,b1,odem,xdim,npts])

[xdot]=chain(t,x)

[z1]=ch_f1(u)

[z2]=ch_f2(u)

Parameters

• f_l : the name of the macro which code the three-species food chain model (default value chain).
• odem,xdim,npts : are optional arguments. Their meaning and syntax can be found in the portr3d help

Description

A call to the function chaintest() will interactively display a phase portrait of a three-species food chain model given by:

 ff1= f1(x(1))
 ff2= f2(x(2))

 xdot1= x(1)*(1-x(1)) - ff1*x(2)
 xdot2= ff1*x(2) -  ff2*x(3) - 0.4*x(2)
 xdot3= ff2*x(3) - 0.01*x(3)
   

and

 f1(u)=5*u/(1+b1*u)
 f2(u)z2=0.1*u/(1+2*u)
   

The default value for b1 is 3.0.

The Scilab macros chain(t,x),f1(u),f2(u) code the dynamical system

See Also

portr3d  ode