Double Pendulum Motion: Plotting theta2 vs Time

[thespaceman]

Hello all,
I have written a python code implementing the Runge-Kutta fourth order method for higher orders to approximate the motion of a double pendulum. The problem I am having is that my plot of theta2 (angle of second rod) Vs time looks a little off and I am curious if I have it correct.
Attached is a graph of both rod angles Vs time. The blue is the first rod and the green is the second rod. I figure the opinion of some physicists may be insightful. Thanks :)
-thespaceman

 

[vanhees71]

It's not so easy to see just from the plot, whether there are numerical problems or not. A good check is, whether the total energy of the system remains conserved in the numerical simulation.