MATLAB: Difficulty solving and plotting solution to complicated second order ODE.

odeode45second order

Hi all,
I am trying to solve quite an ODE that I have formed in my attempt to model the removal of a particle from a thin film. In order to solve this, I am trying to make use of the "odeToVectorField" function in order to break down the second order equation into two first order ODE's.
My script seems to work perfectly, where I can form a MATLAB function of the two first order ODE's, however this is unable to be solved when I call ODE45. I am presented with the following error messages:
Index exceeds matrix dimensions.
Error in symengine>makeFhandle/@(Y,t)[Y(2);(Y(2).*(-6.136363636363637e3))./Y(1)+9.810000000000001]
Error in odearguments (line 87) f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.
Error in ode45 (line 113) [neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, …
Error in furthertests (line 16) sol = ode45(M,[0 20],[1 0]);
I am really not sure why this is occuring. Here is the script that I am currently running:
 clc;
clear; 
D0 = 0.1*10^-9; 
R = 1*10^-6;
m = (4/3)*pi*(R^3)*1100; 
mew = 1.5; 
F0 = m*9.81; 
syms y(t) 
eqn = m.*diff(y,2)== F0 - 6.*pi.*mew.*(R.^2).*(1./y).*diff(y); 
V = odeToVectorField(eqn)
%This breaks down the second order ODE into two separate first order ODE's 
M = matlabFunction(V,'vars',{'Y','t'})
sol = ode45(M,[0 20],[1 0]);
fplot(@(t)deval(sol,t,1), [0, 20])
Apologies for the dodgy spacing in my script, I couldn't figure out how to space it properly on this forum.
Any help you could give with this would be much appreciated.
Cheers.

Best Answer

The time (or other independent variable) has to come first in the argument list of ODE functions.
Reverse them and it works:
M = matlabFunction(V,'vars',{'t','Y'})
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