How do I turn my function into a column vector?

I'm trying to solve a second-order differential equation using matlab, but for some reason I keep getting the error message that my function should be a column vector.

I'm calling the function (tryagain) from the following script (wilyourunnow):

clear all       %Remove stray stuff

ht = linspace(0,10,1001);
h = sin(ht);
%This is based on the instructions as given in the help browser on the page
%for ode45; tab ODE with Time-Dependent Terms

[t,x] = ode45(@(t,x)'tryagain', (0:0.01:10), [0 1]);
plot(t,x)

And this is the function:

function dxdt = tryagain(t,x,ht,h)
h=interp1(ht,h,t);
dxdt = zeros(2, 1);
dxdt(1)= x(2);
dxdt(2) = -x.^2 + x + h;

When I try to run the script, I get the following error:

>> wilyourunnow
Error using odearguments (line 93)
@(T,X)'TRYAGAIN' must return a column vector.

Error in ode45 (line 115)
  odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in wilyourunnow (line 10)
[t,x] = ode45(@(t,x)'tryagain', (0:0.01:10), [0 1]);

I've already tried transposing the vector with these two commands (separately)

dxdt = transpose(dxdt)
dxdt = dxdt(:)

Answer 1

[madhan ravi]

ht = linspace(0,10,1001);
h = sin(ht);
%This is based on the instructions as given in the help browser on the page
%for ode45; tab ODE with Time-Dependent Terms
[t,x] = ode45(@(t,x) tryagain(t,x,ht,h), (0:0.01:10), [0 1]); % change to be noted 
plot(t,x)

function dxdt = tryagain(t,x,ht,h)
h=interp1(ht,h,t);
dxdt = zeros(2, 1);
dxdt(1)= x(2);
dxdt(2) = -x(2).^2 + x(1) + h;   % two x here one has to be x(1) and the other x(2) , you have to correct it according to your equation parameters
end

Gives:

[Wouter Meekes]

Hey madhan,

Thanks for the swift reply. However, the x's that you marked are both supposed to be the position, not one the position and the other the time derivative of the position. Does that still mean that I need one to be x(1) and the other x(2). (Sorry, I've never been good with matlab.)

Furthermore, changing the x's to x(1) and x(2) or both to x(1) doesn't solve the problem either.

Also, Matlab suggested that I say which matlab version I have, but wouldn't let me. I'm using 2018a.

Thanks,

Wouter

[madhan ravi]

Maybe if you post the latex form of the equation maybe I or someone else will help.

[Wouter Meekes]

I realised where it went wrong only after literally copy-pasting your code over my own. When trying to solve the problem myself, I'd tried transposing dxdt (once more after posting the question), but forgot that I input that line. Removing that worked, and now with x replaced by x(1) all is solved.

Thanks a lot!

[madhan ravi]

Anytime :)