Phase space trajectories



Hi, I'm trying to display several trajectories in phase space
corresponding to the same ODEs but with different initial conditions.
I'd also like to use sliders.

I tried to use the "parameters" options in plotdf but it seems you can
only use it for the ODE expressions, not the initial conditions.

So I turned to "manually" do it. I'm using a list of rk to numerically
solve the ODE system and with_slider to draw the trajectories. The code
is like :

load(dynamics);
sol : makelist(rk([-x,v],[v,x],[0,i],[t,0,10,.5]),i,1,3)$
sol_points:makelist(makelist(rest(sol[i][j]),j,1,length(sol[i])),i,1,length(sol));
with_slider(n,makelist(i,i,1,2),[discrete,sol_points[i]]);

but I'm running into the error :

Subscript must be an integer:
i
 -- an error.  To debug this try debugmode(true);

I guess the makelist(i,i,1,2) does not create a list of integers as i
thought it would. How could I fix it ?

Btw if anyone has a simpler way to draw such phase-space trajectories,
I'd be happy to try it.

Thanks for your help.

Julien.