phase space

[Johannes Wolfgang Woger]

Carlo de Falco schrieb:
>
> On 3 Apr 2009, at 14:55, Johannes Wolfgang Woger wrote:
>
>> Hi,
>> I am an newby.
>>
>> How can I obtain a plot of the phase portrait
>> of Lotka-Volterra:
>>
>> octave:92> function xdot = f(x,t)
>>> a = 4;
>>> b = 4;
>>> c = 4;
>>> d = 8;
>>> E = 1;
>>> K = 1;
>>> xdot = zeros(2,1);
>>> xdot(1) = x(1)*(a-b*x(2)-E*x(1));
>>> xdot(2) = x(2)*(d*x(1)-c-K*x(2));
>>> endfunction
>> octave:93>
>> octave:93> t = linspace(0,50,100);
>> octave:94> x = lsode("f", [2,1],t);
>> octave:95> plot(t,x);
>>
>
> plot(x(:,1), x(:,2));
> xlabel("x_1");
> ylabel("x_2");
>
> but I would suggest using a few more time steps if you want a nice 
> looking spiral...
>
Thanks, works great. Is there a tutorial addressing phase space?

>> Thanks
>
> HTH,
> c.
>
>