pendulum(m,k,T,dt)

This function creates a simulation of a mathematical pendulum:
a ball of mass m [kg] is attached to a string of length L [m];
the standard gravity g=9.81 m/s^2;
air resitance is equal to F=-kv^2, where constant k is set by the user;
pendulum oscillates the time period 0..T s;
time step is dt. The outputs are:

a=angle
p=generalized momentum = m*L^2*a'
p/L= real momentum
f=video

example:
[a,p,f]=pendulum(1,0.3,10,0.01);
See a video:
https://www.youtube.com/watch?v=lCPQEAE68TU