Swinging double pendulum in Octave (open source version of Matlab).
Octave can be installed on Linux via sudo apt install octave.
In the unpacked directory just run dp in Octave to start the simulation.
It will plot the double pendulum, which starts swinging after 3 seconds.
The program will first calculate for 2 seconds the time delay necessary to make the pendulum swing in realtime.
On Linux you end the program by typing crtl c.
It uses fourth order Runge-Kutta on the solution of the Hamilton-Lagrange equations.
Parameters can easily be changed at the top of dp.m.
It's fun to set both TH10 and TH20 to 180 degrees.
This gives a vertical double pendulum which should be stable in theory but in practice begins to fall after about a minute due to the finite accuracy of the simulation.
SEE THE DOUBLE PENDULUM IN FULL ACTION IN THE SCREENSHOT BELOW:
