portrait

Scilab Function

portrait - 2 dimensional phase portrait.

[]=portrait(f,[odem,xdim,npts,pinit])

f : a Scilab external which gives the field of the dynamical system. Hence it can be a macro name which computes the field at time t and point x [y]=f(t,x,[u]) or a list list(f1,u1) where f1 is a macro of type [y]=f1(t,x,u) or a character string. The macro can be used to simulate a continuous or discrete system and in case of discrete system the second parameter must be set to 'discrete'
options : The other parameters are optional. If omitted they will be asked interactively
- odem : gives the integration method to use. The value "default" can be used, otherwise see ode for a complete set of possibilities
- npts : a vector of size (2,10) [number-of-points,step] gives the step for integration and the number of requested points. The solution will be calculated and drawn for time=0:step:(step*[number-of-points])
- xdim : [xmin,xmax,ymin,ymax,zmin,zmax] the boundaries of the graphic frame.
- pinit : initial values for integration. A set of initial points can be given in a matrix
```
      pinit = [x0(1), x1(1),...., xn(1)
               x0(2), x1(2),...., xn(2)
               x0(3), x1(3),...., xn(3)].
   
                
```

Interactive integration and display of a 2 dimensional phase portrait of a dynamical system dx/dt=f(t,x,[u]) (where u is an optional parameter )


a=rand(2,2)
deff('[ydot]=l_s(t,y)','ydot=a*y')
portrait(l_s)