Plot2d-Question: How to plot 2 changing functions economically

Try this, it is not very efficient but it is what you asked for.

eq1: 'diff(I,t)=(U-R*I)/L;
eq2: 'diff(I,t)=-(R*I+U)/L;

F(_t, _t0,_R,_L,_U,_eq1,_eq2):=block
(
    [_e1,_e2,_e3,_e4],
    _e1:ode2(_eq1,I,t),
    _e2:ic1(_e1, t=0, I=0),
    _e3:ode2(_eq2,I,t),
    _e4:ic1(_e3, t=_t0, I=rhs(_e2)),
    at(if  t < _t0 then rhs(_e2) else rhs(_e4),[t=_t,R=_R,L=_L,U=_U])
)$

plot2d([F(t,4,2,6,3,eq1,eq2)],[t,0,14]);


-----Original Message----- 
From: Michael Heidinger
Sent: Sunday, January 16, 2011 12:29 PM
To: maxima at math.utexas.edu
Subject: Plot2d-Question: How to plot 2 changing functions 
economically

Hello,
first of all, i'm new to this mailing list - Please excuse my language,
as it's not my first.

Well, I want to simulate an electrical circuit, which has two operation
condition, each of them is discribed with a diffential equation. After a
certain time i want to switch to the other equation.
1. Equation: 'diff(I,t)=(U-R*I)/L (eg. 1 second in this operating
mode=t_equation1)
2. Equation: 'diff(I,t)=-(R*I+U)/L (eg. 2 second in this operation
mode=t_equation2)
Well, I solved them with ode2 and ic1 for some certain points. Eg: t=0
and I=0. But I want to plot I for a longer periode to see how I
develops. I would wish myself a function where I can plot a continous
flow of current.
The function I would wish should look like
I(U,R,L,t,t_equation1,t_equation2).

Dear experts, how can I construct such a function? Thank you in advance
for your help!
Michael Heidinger
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