Pyxplot 
Examples  Pendulum 
Example plot  the motion of a pendulum In this example application of Pyxplot, we use some of its builtin mathematical functions  arcsines and Jacobi functions  to plot the motion of a pendulum which is swinging with an amplitude of 60 degrees. The black lines shows the motion predicted under the assumption of simple harmonic motion, while the red line shows the pendulum's true motion. The small angle approximation is not very good for a pendulum swinging through such a large angle. Scriptset unit angle nodimensionless theta_approx(a,t) = a * sin(2*pi*t) theta_exact (a,t) = 2*asin(sin(a/2)*jacobi_sn(2*pi*t,sin(a/2))) set unit of angle degrees set key below set xlabel r'Time / $\sqrt{g/l}$' set ylabel r'$\theta$' omega = unit(60*deg) plot [0:4] theta_approx(omega,x) title 'Approximate solution', \ theta_exact (omega,x) title 'Exact solution'
