chaintest

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)

`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

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