I am trying to solve a huge system of DAEs. When I start the solution, NDSolve says NDSolve::underdet "There are more dependent variables...". I know about why this error occurs. I have lots of symbols with parameters, and one seems to have the wrong parameters somewhere, so that it is not defined.

My problem is, that in the message the list of variables is shortended like {a,b, <<22>>, y, z}. When I were able to see the whole list, it would give me a hint were to search my syntax error. I tried to use NDSolve`ProcessEquations to get a intermediate state, but this didn't work, same message, no StateData object.

Anyone knows a way to get the whole list?

  • $\begingroup$ Maybe DeleteCases[Derivative[__][_]]@ DeleteDuplicates@Cases[sys, v_[t] :> v, Infinity] -- would give some extraneous things like Cos if Cos[t] were in a coefficient. $\endgroup$
    – Michael E2
    Dec 6, 2019 at 18:42
  • $\begingroup$ This seems better: Internal`ProcessEquations`FindDependentVariables[sys, {t}], where {t} is a list of the independent variable(s). $\endgroup$
    – Michael E2
    Dec 6, 2019 at 18:44
  • 1
    $\begingroup$ See question 134698. $\endgroup$
    – bbgodfrey
    Dec 7, 2019 at 4:55
  • $\begingroup$ @bbgodfrey Thanks a lot, it worked. $\endgroup$
    – axtimhaus
    Dec 7, 2019 at 9:28


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