Too many output arguments ode23t

I am using this function

function maxh_d(t,x)
dxdt = zeros(2,1); % x(1) refers to x ,x(2) refers to p
dxdt(1)= -x(1) ; %+u
dxdt(2)= 2*x(1)*x(2);
end

in this code

[t_v,x_v] = ode23t(@(t,x) maxh_d(t,x), [0 10], [0.5 0.5]);

figure('Name','Nonlinear');
subplot(2,1,1)
plot(t_v, x_v(:,1));

I am getting this error

Error using maxh_d
Too many output arguments.

Error in mh_result>@(t,x)maxh_d(t,x) (line 1)
[t_v,x_v] = ode23t(@(t,x) maxh_d(t,x), [0 10], [0.5 0.5]);

Error in odearguments (line 90)
f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.

Error in ode23t (line 143)
    odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in mh_result (line 1)
[t_v,x_v] = ode23t(@(t,x) maxh_d(t,x), [0 10], [0.5 0.5]);

Answer 1

[Bjorn Gustavsson]

Try to change your maxh_d function to explicitly return dxdt:

function dxdt = maxh_d(t,x)
dxdt = zeros(2,1); % x(1) refers to x ,x(2) refers to p
dxdt(1)= -x(1) ; %+u
dxdt(2)= 2*x(1)*x(2);
end

I've always written my ODE-functions so that they return the derivative. How you get that error-message I've no idea - since to my understanding 0 output arguments are one too few...

HTH

[Stephen23]

"How you get that error-message I've no idea - since to my understanding 0 output arguments are one too few..."

The slightly ambiguous message is from the perspective of how the function is called, i.e. it is being called with more output arguments than the function can provide:

[X] = max(A); % okay
[X,Y] = max(A); % okay
[X,Y,Z] = max(A); % -> Too many output arguments.

If the function can provide zero outputs, then clearly requesting just one will be "too many".

[Bjorn Gustavsson]

...Ah, perhaps I should spend some time reading and thinking before answering...

[Stephen23]

@Bjorn Gustavsson: I agree that the message is ambiguous. Perhaps it should be expanded a little to clarify, e.g.: "Too many output arguments requested", or similar.