error with using ode45

Question

Devyani 2014-10-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/159066-error-with-using-ode45

评论： Devyani 2014-10-18

i am writing this simple code and it is showing error as below... i dont knw why i am using matlab 2011b

function dydt = react(t,y)
% Solve the kinetics example
dydt = zeros(size(y));
% Parameters
k1 = 5; k2 = 2; k3 = 1;
A = y(1);
B = y(2);
C = y(3);
dydt(1) =k1*A + k2*B;
dydt(2) = k1*A*(k2+k3)*B;
dydt(3) = k3*B;

error is as follows

Error using feval
Undefined function 'react' for input arguments of type 'double'.
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, ...

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Answer 1

Kelly Kearney 2014-10-17

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https://ww2.mathworks.cn/matlabcentral/answers/159066-error-with-using-ode45#answer_155606

How are you calling ode45? And where did you save the reac.m function? The error indicates that ode45 isn't seeing the react function it on your path, and therefore can't apply the solver to it.

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Devyani 2014-10-17

my file is in the same folder which is open.i am using ode45 as follows:

[t,c]=ode45('react',[0 5],[1 0 0]);

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Answer 2

Star Strider 2014-10-17

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https://ww2.mathworks.cn/matlabcentral/answers/159066-error-with-using-ode45#answer_155607

在 MATLAB Online 中打开

You need to include an ‘@’ sign to create a function handle for ‘react’ in your ode45 call:

[t,y] = ode45(@react, tspan, y0);

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Star Strider 2014-10-18

I am happy you got it running. I had no problems at all running your ‘react’ ODE function with the ode45 call I used. It ran perfectly for me in R2014b. Did you change your ode45 call to what I suggested, or did you keep it as in your original code?

Devyani 2014-10-18