Keep getting this error and I cannot figure out why: Dimensions of arrays being concatenated are not consistent.

I have the following code trying to solve differential equation of second order:

[t,X] = ode45(@(t,X) odefun_4(t,X,u), [0 10], [0;0]);

function dx = odefun_4(t,x,u)
    %xdisp(u);
    m = 15;
    b = 0.2;
    k = 2;
    %u = interp1(ut,u,t);
    dx = [x(2); u/m - (b/m)*x(2) - (k/m)*x(1)];

end

Vector u is a 1x100 vector. I expect to get a 2x100 matrix as the return value. What am I doing wrong ?

Answer 1

[madhan ravi]

EDITED

m = 15;
b = 0.2;
k = 2;
ut = linspace(0, 10);
u = 5 * sin(2 * ut) + 10.5; % input of our system - external forc
dx = @(t,x,u)[x(2); u/m - (b/m)*x(2) - (k/m)*x(1)]

for u=u
[t,X] = ode45(@(t,x)dx(t,x,u), [0 10], [0;0]); %function calling
plot(t,X)     
hold on
end

[madhan ravi]

u must be a scalar

[Teo Protoulis]

Why scalar ? I am simulating a system and I want to get one output value for each input value.

[madhan ravi]

provide u values , plus your solution returns is 57 by 2 matrix how can you concatenate 1 by 100 in that matrix ?

[Teo Protoulis]

u is created like this:

ut = linspace(0, 10);
u = 5 * sin(2 * ut) + 10.5; % input of our system - external force

[madhan ravi]

see edited answer

[Teo Protoulis]

Tried the edited version of your answer and got this:

@(T,X)ODEFUN_4(T,X,U) returns a vector of length 1, but the length of initial conditions vector is 2. The vector returned by @(T,X)ODEFUN_4(T,X,U) and the initial conditions vector must have the same number of elements.

[madhan ravi]

Did you try my edited answer? I got the graph. Make sure to accept the answer if you got the answer to your question.

[Teo Protoulis]

Yes, now I got the graph. I wonder why I don't get 100 values as output since I use 100 values as input.

[madhan ravi]

Each plot represents the change in the system according to each force this is the only way to solve your problem because the reason is like I told you before you can't put column vector with 100 values into a matrix of lesser column elements

[Teo Protoulis]

Thank you very much!

[madhan ravi]

Anytime :) make sure to accept the answer so that people know the question is solved