error with using ode45

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Devyani
Devyani on 17 Oct 2014
Commented: Devyani on 18 Oct 2014
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, ...

Answers (2)

Kelly Kearney
Kelly Kearney on 17 Oct 2014
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.
  1 Comment
Devyani
Devyani on 17 Oct 2014
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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Star Strider
Star Strider on 17 Oct 2014
You need to include an ‘@’ sign to create a function handle for ‘react’ in your ode45 call:
[t,y] = ode45(@react, tspan, y0);
  5 Comments
Star Strider
Star Strider on 18 Oct 2014
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
Devyani on 18 Oct 2014
I kept it with my riginal code... i deleted the file.. closed matlab and the again created the function file after sometime.. it workd... :p

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