ode45 not enough input argument

Hi everyone, i have a problem with an ode function, i show you the code:

%Ode function:

function dTdt=ode1(t,T,d,e)

dTdt=d-e*T

return

%main code

T0=293;

T1=400;

Tf2=293;

a=0.2;

tchange=(T1-T0)/a;

for t=1:(tchange)+1

    Tf(t)=T0+a*(t-1);

    d=(Tf(t)-Tf2)/(R*C)

    e=-2/(R*C)

[t,T] = ode45(ode1,[0 336],293,d,e)

end

Matlab says to me:

Error using ode1 (line 2) Not enough input arguments.

Error in Untitled (line 27) [t,T] = ode45(ode1,[0 336],293,d,e)

i know that i have to put some value for d and e, but how can i do if they change every step because they are in a for cycle? What else is wrong? Please please help me, i can't do anything by myself!

Answer 1

[Mischa Kim]

saramatlab, use

 function my_ode()
 %main code
 T0  = 293;
 T1  = 300;
 Tf2 = 293;
 a   = 0.2;
 R   = 1;   % not defined in your code
 C   = 1;   % not defined in your code
 tchange = (T1-T0)/a;
 for ii = 1:(tchange)+1
    Tf(ii) = T0 + a*(ii-1);
    d      = (Tf(ii) - Tf2)/(R*C);
    e      = -2/(R*C);
    % d and e need to be passed as parameters
    [t,T]  = ode45(@ode1,[0 336],293,[],[d,e]);
 end
 end

 function dTdt = ode1(t,T,param)
 d    = param(1);
 e    = param(2);
 dTdt = d - e*T;
 end

Put both functions in the same function file and name it my_ode.m. The code is in no way optimized, but runs properly.

[saramatlab]

Thank you so much, it works!!! :):):) Can i ask you another one question? i've to compare my solution with one other,i have to check that at the end my ode function this relationship: a*t+293=400 is true.

t is the same variable that i have in the ode, how can i put in my ode function this relationship so that t is the same for both the equation?

Answer 2

[Andy L]

You need to vectorise your inputs to ode1 as below:

%Ode function:
function dTdt = ode1(t,T,d,e)

becomes

function dTdt = ode1(t,Y)
Y(1) = T;
Y(2) = d;
Y(3) = e;

Check example 1 in this link ode45

[saramatlab]

Thank you so much, i've done what you said, i write here how i changed my file:

%ode function:

function dTdt=ode1(t,Y)
Y(1) = T;
Y(2) = d;
Y(3) = e;
dTdt=Y(2)-Y(1)*Y(3)
end

%Main program:

T0=293;
T1=400;
Tf2=293;
a=0.2;
tchange=(T1-T0)/a;

for t=[1:tchange+1]
    Tf(t)=T0+a*(t-1);
    d=(Tf(t)-Tf2)/(R*C);
    e=-2/(R*C)
    [t,T]=ode45('ode1',[1 366],[293 0 -4.7824e-005])
end

Now matlab signal this:

Error using ode1 (line 2)
Not enough input arguments.

Error in odearguments (line 88)
f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.

Error in ode45 (line 114)
[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...

Error in Untitled (line 29)
    [t,T]=ode45('ode1',[1 366],[293 0 -4.7824e-005])

How can i fix it?

[Andy L]

A few things to consider:

• When is T declared?
• When is Y declared?
• Should T be a vector?
• How are you storing the results of your optimisations?

[saramatlab]

T is the variable that i want to calculate with the differential equation, it's a temperature profile and i only know its initial value. I am not storing the results beacuse i'm not able to :(

Answer 3

[saramatlab]

Can i ask you another one question? i've to compare my solution with one other,i have to check that at the end my ode function this relationship: a*t+293=400 is true.

t is the same variable that i have in the ode, how can i put in my ode function this relationship so that t is the same for both the equation?