Error in ode45

i am trying to solve using ode45, however getting error:

Error using odearguments

Inputs must be floats, namely single or double.

Error in ode45 (line 107)

odearguments(odeIsFuncHandle,odeTreatAsMFile, solver_name, ode, tspan, y0, options, varargin);

Error in coupled_ode (line 15)

[t,y] = ode45(ftotal, tspan, ic);

Error in Main (line 13)

[y]=coupled_ode(O, a, g, L, eta, eta_tos ,t_o,T_forced);

I conducted study without "t_o", I got quite good results, but may be getting error due to t_o.

Answer 1

[VBBV]

As error suggests that inputs must be of type 'double' , there is a symbolic variable declaration for variable t_o inside the function which is passed as tspan input to ode45. Its possible to avoid such difference by passing the variable directly when calling the function

rng("default")
clc;
close all;

O=rand;
a=rand;
g=9.81;
L=rand;
eta=0.46;
eta_tos=1;
t_o=5;
T_forced=pi/eta_tos;
[t,y]=coupled_ode(O, a, g, L, eta, eta_tos ,t_o,T_forced)

t = 101×1

5.0000 5.0314 5.0628 5.0942 5.1257 5.1571 5.1885 5.2199 5.2513 5.2827

y = 101×4

0 1.0000 0 1.0000 0.0304 0.9210 0.0325 1.0533 0.0571 0.7718 0.0653 1.0219 0.0783 0.5670 0.0958 0.9056 0.0924 0.3255 0.1214 0.7114 0.0986 0.0685 0.1398 0.4529 0.0967 -0.1823 0.1494 0.1494 0.0874 -0.4068 0.1490 -0.1752 0.0716 -0.5874 0.1384 -0.4950 0.0511 -0.7111 0.1182 -0.7838

figure
plot(t, y)
grid
legend('y','Dy','x','Dx')

function [t,y] = coupled_ode(Onum, anum, gnum, Lnum, eta_num, eta_tos_num ,t_o,T_forced)
  syms O a g L x(t) y(t) t Y eta_tos eta
  dx = diff(x);
  d2x = diff(x,2);
  dy = diff(y);
  d2y = diff(y,2);
  Eq1 = d2x == 2*O*sin(a)*dy - (g/L)*x(t)-sin(eta_tos*t_o)+sin(eta*t);
  Eq2 = d2y == -2*O*sin(a)*dx - (g/L)*y(t);
  [VF,Subs] = odeToVectorField(Eq1, Eq2);
  VF = subs(VF,[O a g L eta eta_tos t_o],[Onum anum gnum Lnum eta_num eta_tos_num t_o]);
  ftotal = matlabFunction(VF,'Vars',{t,Y});
  tspan = [t_o:T_forced/100:(T_forced+t_o)];                                             % Choose Appropriate Simulation Time
  ic = [0 1 0 1];                                            % Choose Appropriate Initial Conditions
  [t,y] = ode45(ftotal,(tspan), ic);
  
end

[Susmita Panda]

Got it....Thanks a lot..