Re: Non homogeneous differential equations

[John W. Eaton]

On 22-May-2007, François Poulain wrote:

| Thank you for your help, but it doesn't work in octave : you can see the
| computation below. I already tried some things like that, and I didn't
| find any way to solve this problem ...
| 
| octave:1> function xdot = f (x, t, uf, tauf)
| >   persistent a = 1
| >   persistent b = 1
| >   u = uf (t);
| >   xdot = [-a*x(4)*sin(x(3))+u(1);
| >           -a*x(4)*cos(x(3))+u(2);
| >           -x(4)+u(3);
| >           b*(x(1)*sin(x(3))+x(2)*cos(x(3)))-tauf(t)];
| > endfunction
| octave:2>  t = linspace (0, 1, 101);
| octave:3>  x = lsode (@ (x, t) f (x, t, @ (t) t.^((0:2)'), @sin), zeros
| (4, 1),t);
| error: lsode: first arg should be a string or 2-element string array
| error: evaluating assignment expression near line 3, column 4

Newer versions of Octave will handle this.

jwe