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!
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Walter Roberson
2018년 1월 7일
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.
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Jan
2013년 5월 14일
편집: Jan
2013년 5월 14일
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.
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