Error using ode45 for spring pendulum

Hello there, I was developing an example for class of a spring pendulum that was to utilize the ode45 command on MATLAB. Problem is, that somehow the ode45 keep encountering errors and I can't seem to figure out why this is the case. Anyone have any insight?

[madhan ravi]

Could you paste the code(not as a file)?

[Mathew Amador]

"Solve for the EOMs of a spring pendulum system, then integrate the EOM for 10 seconds starting at rest with the radial position at and . The spring is unstretched at . Then, integrate the EOM for 120 seconds starting at rest with a variety of initial conditions with in meters and in degrees."

Goal: Plot the initial position of the mass using a blue line with 'x' markers and the final position of the mass using a black line with 'x' markers.

Step 1:

clear variables
clc
m = 0.1416;  % kg
k = 7.1;     % N/m
g = 9.81;    % m/s^2
r_0 = 9;     % cm
r = 29;      % cm
theta = 30;  %degrees

Step 2:

List variables:

m: mass,

k: spring constant,

r: radius,

r_0 : unstretched radius,

theta : Initial angular displacement,

g: gravity,

r_m: linear displacement of mass in the r-direction, state variable

r_mddot: accelerations (EOMs) of the mass in the r-direction

theta_m: displacement of mass in the -direction, state variable

theta_mddot: accelerations (EOMs) of the mass in the -direction

Step 3:

syms m l r 
syms thetadot thetaddot rdot rddot
eqn(1) = m*thetaddot == m*((l+r)*thetaddot+2*rdot*thetadot);
eqn(2) = m*rddot == m*(rddot-(l+r)*thetadot^2);

Step 4:

Find Unknown variables

theta double dot, and r double dot : accelerations in the theta and r directions, respectively

2 equations, 2 unknowns

Step 5:

unknowns = solve(eqn, rddot, thetaddot)
accelEOMs = solve(eqn,rddot,thetaddot);
accelEOMs = struct2cell(accelEOMs);

Step 6:

Solve equation of motion (EOM)

[T,S] = ode45(@(t,s)eom(m, k, r, r_0, theta, g),linspace(0,10,100),[0,0]);

[darova]

Something is wrong