I split these problems into three tickets, now trac #9823, #9824, and
#9825. My knowledge and need are not great enough for me to dig into
these at the moment, but at least they are in the system now. :-)
- Ryan
On Aug 27, 6:05 am, "ma...@mendelu.cz" <ma...@mendelu.cz> wrote:
> Both desolve_system and desolve_laplace use Maxima's function desolve.
> Desolve_laplace has been updated in 2009, but desolve_system not. I
> believe that desolve_system could be improved in the same way as
> desolve_laplace. Please, make a trac report and put me (robert.marik)
> into Cc field. Thanks
>
> Robert
>
> On 26 srp, 23:25, Ryan Hinton <iob...@email.com> wrote:
>
> > I am having trouble trying to use desolve_system. Am I doing
> > something wrong? If not, I can create trac tickets for these errors.
>
> > 1. If I make the reference manual example easier, I get an exception:
>
> > sage: t = var('t')
> > sage: x = function('x', t)
> > sage: de1 = diff(x,t) + 1 == 0
> > sage: desolve_system([de1], [x])
> > ...
> > TypeError: unable to make sense of Maxima expression '(x(t)=x(0)-t)
> > [1]' in Sage
>
> > 2. Initial conditions are apparently ignored.
>
> > sage: t = var('t')
> > sage: epsilon = var('epsilon')
> > sage: x1 = function('x1', t)
> > sage: x2 = function('x2', t)
> > sage: de1 = diff(x1,t) == epsilon
> > sage: de2 = diff(x2,t) == -2
> > sage: desolve_system([de1, de2], [x1, x2], ivar=t)
> > [x1(t) == epsilon*t + x1(0), x2(t) == -2*t + x2(0)]
> > sage: desolve_system([de1, de2], [x1, x2], ics=[1,1], ivar=t)
> > [x1(t) == epsilon*t + x1(0), x2(t) == -2*t + x2(0)]
>
> > 3. Making the example nonlinear, I get a different exception.
>
> > sage: t = var('t')
> > sage: x1 = function('x1', t)
> > sage: x2 = function('x2', t)
> > sage: de1 = (diff(x1,t) == -3*(x2^2-1))
> > sage: de2 = (diff(x2,t) == 1)
> > sage: desolve_system([de1, de2], [x1, x2], ivar=t)
> > ...
> > TypeError: unable to make sense of Maxima expression 'x1(t)=ilt(-
> > ((3*laplace(x2(t)^2,t,?g1543)-x1(0))*?g1543-3)/?g1543^2,?g1543,t)' in
> > Sage
>
> > In the process of putting in my full, complicated example, I found the
> > bug that produced yet another, confusing exception. :-)
>
> > Any guidance or suggestions are appreciated. Thanks!
>
> > - Ryan
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