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Re: Help need for Differential algebraic equations
From: |
genehacker |
Subject: |
Re: Help need for Differential algebraic equations |
Date: |
Fri, 10 Oct 2008 14:30:20 -0700 (PDT) |
thanks very much for the help. now it defnitely works:)
genehacker wrote:
>
> Hi all,
>
> I am new to octave and i love it the best as an open source
> alternative to matlab. I used lsode to solve ordinary diff equations, but
> now I do also have some algebraic equations to solve along.
>
> I came across this function 'dassl', which is supposed to solve
> differential algebraic equations, but have problems using it. This is how
> i use it currently and below is the error message. I have no idea what it
> is. Please help!
>
> ******code*****
>
> function xdot = f(x,xdot,t);
> %define all parameter values viz. k12, k23,f86 etc here
> xdot = zeros(9,1);
> xdot(2) = k12*x(1) - k23*x(2);
> xdot(3) = k23*x(2);
> xdot(5) = k45*x(4) - k56*x(5);
> xdot(6) = k56*x(5) - k67*x(6);
> xdot(7) = k67*x(6);
>
> x(8) = f86*x(6);
> x(9) = f29*x(2);
> endfunction;
>
>
> x0 = ones(9,1)';
> xdot0 =zeros(9,1)';
> t = linspace(0,50,50);
> dassl("f",x0,xdot0,t)
>
> *****output******
>
> ***MESSAGE FROM ROUTINE DDASSL IN LIBRARY SLATEC.
> ***POTENTIALLY RECOVERABLE ERROR, PROG ABORTED, TRACEBACK REQUESTED
> * AT T = 0.000000E+00 AND STEPSIZE H = 1.594388E-05 THE
> ITERATION
> * MATRIX IS SINGULAR
> * ERROR NUMBER = -8
> *
> ***END OF MESSAGE
>
> ***JOB ABORT DUE TO UNRECOVERED ERROR.
> 0 ERROR MESSAGE SUMMARY
> LIBRARY SUBROUTINE MESSAGE START NERR LEVEL COUNT
> SLATEC DDASSL AT T = 0.000000E+ -8 1 1
>
> error: exception encountered in Fortran subroutine ddassl_
> error: caught execution error in library function
>
--
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