Re: ode45 issue: dimension mismatch

[Sebastian Schöps]

Tweetman wrote
> Hello, sorry for the confusion. Yes, what I meant was
> dx/dt = M*(x^m)*(1-x)^n

If the initial value is x(0)=0 then your ODE will only have the trivial
solution x=0. 


Tweetman wrote
> clear; clc;
> t = linspace(0,400,101);
> x0 = [0, 0];
> function f = dx(x,t)
> M = 2.933e-5;
> m = 0.158;
> n = 1.26;
> dx = M*(x.^m)*(1-x).^n;
> endfunction
> [t,x] = ode45(@dx, t, x0);

* I suggest to use a anonymous function, see
https://www.gnu.org/software/octave/doc/v4.2.0/Anonymous-Functions.html
* Your initial value as two components but it is a scalar ode

Try this:

t = linspace(0,400,101); 
x0 = 0; 
M = 2.933e-5; 
m = 0.158; 
n = 1.26; 
dx = @(t,x) ( M*(x.^m)*(1-x).^n ); 
[t,x] = ode45(dx, t, x0);
plot(t,x)

and enjoy the zero function :)

Seb.



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