ode45 not enough input argument

Question

saramatlab 2014-9-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/153998-ode45-not-enough-input-argument

编辑： saramatlab 2014-9-9

采纳的回答： Mischa Kim

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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!

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Answer 1

Mischa Kim 2014-9-8

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/153998-ode45-not-enough-input-argument#answer_151059

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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.

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saramatlab 2014-9-8

编辑：saramatlab 2014-9-9

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?

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Answer 2

Andy L 2014-9-8

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/153998-ode45-not-enough-input-argument#answer_151027

编辑：Andy L 2014-9-8

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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

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Andy L 2014-9-8

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 2014-9-8

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 :(

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Answer 3

saramatlab 2014-9-9

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/153998-ode45-not-enough-input-argument#answer_151124

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?