Using ODE45 on inverted pendulum without external torque
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I have this problem, I'm trying to plot my solutions but there is an error not enough input arguments. The question is in the attached file.
function dx = invpen(t,x)
dx = zeros(2,1); % column vector
dx(1) = x(2);
dx(2) = (1/(1.0*1.0^2))*(1.0*9.8*1.0*sin(x(1)-0.5*x(2)));
[T,X] = ode45(@invpen,[0,20],[30,0]);
plot(T,X(:,1),'-',T,X(:,2),'.')
1 Comment
Jan
on 12 Sep 2018
Is this stored in one file and you start it using the "Start" button of the editor? Then invpen is called without inputs.
Answers (2)
Stephan
on 12 Sep 2018
Hi,
use:
[T,X] = ode45(@invpen,[0,20],[30,0]);
plot(T,X(:,1),'-',T,X(:,2),'.')
function dx = invpen(~,x)
dx = zeros(2,1); % column vector
dx(1) = x(2);
dx(2) = (1/(1.0*1.0^2))*(1.0*9.8*1.0*sin(x(1)-0.5*x(2)));
end
The code runs so far - i did not check if it is a meaningful result.
Best regards
Stephan
3 Comments
Stephan
on 12 Sep 2018
Glad to hear - Please accept helpful answers in order to help other people having similar problems finding helpful answers.
Jan
on 12 Sep 2018
Is this stored in one file and you start it using the "Start" button of the editor? Then invpen is called without inputs.
Stephen's suggestion should work. Create a file called "main.m" (or whatever you like) and insert the code. Then you can start this as a script from the command window or with the "Start" button. Defining subfunctions inside scripts works in modern Matlab versions only. For an older version start the "main.m" file with
function main
3 Comments
Jan
on 13 Sep 2018
@Stephan: This feature was introduced in R2016b: https://www.mathworks.com/help/matlab/matlab_prog/local-functions-in-scripts.html
By the way: Answers: Search for "subfunctions in scripts" ;-)
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