ODE45 issues (odearguements error)

Hi recently I've started having to use the ode45 function for various classes I have taken, I think I understand how to format the inputs to the solver, or atleast I thought I did.

Error using odearguments (line 93)
@(T,Y)VELOCITY(T,Y,A,P_0,Y_0,GAMMA,M) must return a column
vector.

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

Error in currentproblem (line 20)
[t,y] = ode45(@(t,y)velocity(t,y,A,P_0,y_0,gamma,m), timespan,
IC);

This error is occuring from what I have here:

%Constants (Initial conditions)
%  A  = area (m^2)
% P_0 = original pressure (Pa)
% x_0 = original distance from left edge of the gun. (m)
%  x  = distance after block is released (m)
%  m  = mass of block (kg)
% gamma = air constant (unitless)
% t = time (s)
m = 0.1; %kg
y_0 = 1; %m
P_0 = 5000;%Pa
A   = 0.1; %m^2
gamma = 1.4; %air constant
IC = [m y_0 P_0 A gamma];
timespan = 0:0.0001:0.2;

[t,y] = ode45(@(t,y)velocity(t,y,A,P_0,y_0,gamma,m), timespan, IC);

The function it's calling is this:

function v = velocity(t,y,A,P_0,y_0,gamma,m)
%Velocity of a block within enclosed space given various parameters

v= sqrt((2*A*P_0*(y_0^gamma).*y)/((y.^gamma).*m*(1-gamma)));
end

Now one thing I can spot off the bat is that I have the function calling for 't' (time) with no 't' variable, but the documentation I was reading said this would be alright and that the ode45 calls the first 2 variables (i.e t and y in this case). I've tried various things such as have y be defined in terms of givens etc and I just can't seem to get the solution through the ode45 command and I was just wondering if another set of eyes could point me in the right direction.

As always I appreciate any all help!

Answer 1

[darova]

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