ode45 - return a column vector
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Below is the function i have described:
function ssir = fnsir(t,y)
b = 0.1;
q = 0.022;
m = 0.012;
l = 0.125;
r = 0.14;
ssir(1) = q - m*y(1)-b*y(1)*y(2)+ l*y(3);
ssir(2) = (b*y(1)*y(2))-((m+r)*y(2));
ssir(3) = (r*y(2)) - (y(3)*(m+r));
------------------------------
And i am calling this function using:
[t,y]=ode45('fnsir', [0 10], [200 20 2])
and i am getting the following error:
??? Error using ==> odearguments at 113 FNSIR must return a column vector.
Error in ==> ode45 at 173 [neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...
--------------------------
can anyone please help me sort this out
Thanks!
3 Comments
Walter Roberson
on 7 Jan 2018
SAFA BOUDHRAA: As the very last step of your function, turn the output into a column vector. For example if you currently have
function dy = MyOde(....)
...
dy = ....
then after that do
dy = dy(:);
as the last thing before returning. The variable you should do this to is the one returned by your function.
If that does not work, then use the debugger to check whether possibly you are returning the empty vector.
Accepted Answer
Jan
on 14 May 2013
Edited: Jan
on 14 May 2013
ODE45 expects the reply as [3 x 1] vector, but your code creates a [1 x 3] vector. Two solutions:
1. Pre-allocate ssir as a vector of the wanted shape:
ssir = zeros(3, 1);
ssir(1) = ...
2. Or append a reshaping as last line of the function fnsir:
ssir = ssir(:);
As you see, the error message is rather clear. It is worth to read Matlab's messages carefully. They are the best messages I've ever seen in a commercial software.
8 Comments
Ali Amirfaridi
on 28 Apr 2020
Edited: Ali Amirfaridi
on 30 Apr 2021
still helping in 2020! thank you mate
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