even for the 1st order ODE, y must be a vector.
(and, apparently, for y as well)
The following example works:
sage: t,y=var('t,y');
....: g= lambda t,y:[-y[0]]; # ODE y'=-y
....: ra = ode_solver();
....: ra.function=g;
....: ra.ode_solve(y_0=[1],t_span=[0,1],num_points=100)
Now, if I change g to
g= lambda t,y:[-y[0]/(2*y[0]^3 - 1)];
the example runs, but seemingly never stops. Perhaps you hit a singularity
somewhere that results in
such a non-convergence.
On Monday, November 17, 2025 at 10:21:42 AM UTC-6 Dima Pasechnik wrote:
> On Mon, Nov 17, 2025 at 3:45 AM [email protected] <[email protected]> wrote:
>
>> According to the manual the following should work:
>>
>> t,y=var('t,y');
>> g= lambda t,y:-y/(2*y^3 - 1);
>> ra = ode_solver();
>> ra.function=g;
>> ra.ode_solve(y_0=1,t_span=[0,1],num_points=100)
>>
>
>
> Please write the ODE you want to solve, in the usual maths notation -
> it's not clear what it is.
>
>
>
>>
>> However, I get the error message
>>
>>
>> ---------------------------------------------------------------------------
>> TypeError Traceback (most recent call last)
>> /tmp/ipykernel_317/557462051.py in <module> ----> 1 ra.ode_solve(y_0=
>> Integer(1),t_span=[Integer(0),Integer(1)],num_points=Integer(100))
>> /usr/lib/python3/dist-packages/sage/calculus/ode.pyx in
>> sage.calculus.ode.ode_solver.ode_solve
>> (build/cythonized/sage/calculus/ode.c:5124)() 412 self.y_0 = y_0 413 -->
>> 414 dim = len(self.y_0) 415 type = isinstance(self.function,ode_system)
>> 416 if type == 0: TypeError: object of type 'sage.rings.integer.Integer'
>> has no len()
>>
>> Also
>> def f(t,y): return -y/(2*y^3 - 1);
>> ra.function=f;
>>
>> gives the same error.
>>
>> ??
>>
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>>
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