Re: lsode problems

[Thomas D. Dean]

On 07/24/2016 08:00 AM, CarlB wrote:
> I have been messing with lsode for a few days and I just can't get it to
> function without errors.
> *M-file:*
> clear all
> clc
>
> % Time span
> tspan = [0 1]';
>
> % Initial Conditions
> IC = [0 0]';
>
> % ODE Solver
> [z,t] = lsode(@odem5,tspan,IC)
>
> *Function*
> function zdot = odem5(z,t)
>
>
> %% if statement for step input f
> if t < 0
>      f = 0
> elseif 0 < t >= .4
>      f = 600
> else
>      f = 0
> endif
>
> zdot = zeros(2,1);
> zdot(1) = z(2);
> zdot(2) = (-12*z(2) - 900*z(1) + .15*f);
> endfunction
>
> *This returns the error:*
>   LSODE--  REPEATED CALLS WITH ISTATE = 1 AND TOUT = T (=R1)
>        In above message,  R1 =  0.0000000000000D+00
>   LSODE--  RUN ABORTED.. APPARENT INFINITE LOOP
> f = 0
> error: lsode: exception encountered in Fortran subroutine dlsode_
> error: called from
>
> any help would be great,
>
> Gus
>
>
>
> --
> View this message in context: 
> http://octave.1599824.n4.nabble.com/lsode-problems-tp4678790.html
> Sent from the Octave - General mailing list archive at Nabble.com.
>
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> version
ans = 4.0.2

clear all
function zdot = odem5(z,t)
if t < 0
f = 0;
elseif 0 < t >= .4
f = 600;
else
f = 0;
endif;
zdot = zeros(2,1);
zdot(1) = z(2);
zdot(2) = (-12*z(2) - 900*z(1) + .15*f);
endfunction;

tspan = [0 1]';
IC = [0 0]';
[z,t] = lsode(@odem5,tspan,IC);

> z
z =

0 1
0 1
> t
t = 1

Tom Dean