I keep getting an error. Help

%This progrem will use dfuncl.m

tspan = 0: 0.05: 8;

y = [0.4; 0;0];

[t , y]= ode23(@odefun, tspan, y);

plot (t, y(:, 1));

xlabel ('t');

ylabel ('y(1');

title ('problem 2.187');

function f = odefun( ~ , y )

u = 0.5;

k = 100;

m = 5;

f=zeros(2,1);

f(1) = y(2);

f(2) = -u*9.81*sign(y(2))-k*y(1)/m;

end

---------------------------------------------------------------

An error occurred while using the note: odarguments (line 95)

ODEFUN returns a vector of length 2, but the initial condition vector is of length 3.

The vector returned by ODEFUN and the initial condition vector must have the same number of elements.

Error occurred: ode23 (line 114)

odarguments(FcnHandlesUsed, solver_name, ode, tspan, y0,

options, varargin);

Error occurred: pr187 (line 5)

[t , y]= ode23(@odefun, tspan, y);

Answer 1

[VBBV]

tspan = [0:0.05: 8];
y = [0.4; 0];
[t , y]= ode45(@odefun, tspan, y);
plot (t, y(:, 1));
xlabel ('t');
ylabel ('y(1');
title ('problem 2.187');

function f = odefun( ~ , y )
u = 0.5;
k = 100;
m = 5;
f=zeros(2,1);
f(1) = y(2);
f(2) = -u*9.81*sign(y(2))-k*y(1)/m;
end

check with ode45