Re: lsode problems

[Tatsuro MATSUOKA]

> From: CarlB 

> To: help-octave
> Cc: 
> Date: 2016/7/25, Mon 00:00
> Subject: lsode problems
> 
> 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
> 
From manual



if (condition)
  then-body
elseif (condition)
  elseif-body
else
  else-body
endif

if startements require ().


What is this? Apparently odd
0 < t >= .4


You would like to mean
( (0<t) & (t<=.4) )
right ? (& is required.)  )


Perhaps the below is correct for if block

if (t < 0) 
    f = 0;
elseif ((0 < t) &  (t <= .4))
    f = 600;
else 
    f = 0;
endif



Tatsuro