desolve_system error "unable to make sense of Maxima expression"

asked 2012-11-30 00:51:59 -0500

petres gravatar image
t = var('t')

y = function('y', t)
w = function('w', t)
p = function('p', t)

de1 = diff(y,t) == - 0.5*y - 0.9*p + 0.5*w
de2 = diff(w,t) ==           1.0*p + 0.7*w
de3 = diff(p,t) == + 0.5*y         - 0.3*w

desolve_system([de1, de2, de3], [y,p,w])

The function desolve_system stops with the error:

TypeError: unable to make sense of Maxima expression 'y(t)=ilt((200y(0)?g1090327^2+(-140y(0)+100w(0)-180p(0))?g1090327+60y(0)+54w(0)+226p(0))/(200?g1090327^3-40?g1090327^2+80?g1090327-83),?g1090327,t)' in Sage

Why? Thanks in advance!

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Comments

Same holds also with ivar and ics arguments in desolve_system.

petres gravatar imagepetres ( 2012-11-30 00:58:06 -0500 )edit
kcrisman gravatar imagekcrisman ( 2012-11-30 02:01:05 -0500 )edit

Thanks for the answer. It is a little disappointing. Is there a workaround? Maybe I could solve it in another way with Sage (using the e-function for matrizes ...) or by using directly the Maxima functions.. Without being able to solve linear differential equations I would have to switch to other math programms.

petres gravatar imagepetres ( 2012-12-02 22:26:51 -0500 )edit

Those both sound like good workarounds. As noted in the ticket, this is really an upstream problem to some extent; we should not see the `?g123` type symbols.

kcrisman gravatar imagekcrisman ( 2012-12-03 06:34:42 -0500 )edit

It seems like the worst problem here may have been solved upstream, see https://sourceforge.net/p/maxima/bugs/2774/

kcrisman gravatar imagekcrisman ( 2014-11-03 08:05:18 -0500 )edit