return f
#pend_mod=Explicit_Problem(f, y0=np.array([1, 1, 0, 0] ))
#pend_mod.problem_name='Nonlinear Pendulum'
#Define an explicit solver
#exp_sim = CVode(pend_mod) #Create a BDF solver
#t, y = exp_sim.simulate(1)
rhs = getRHS(100)
pend_mod=Explicit_Problem(rhs, y0=np.array([2, 2, 0, 0]))
pend_mod.problem_name='Nonlinear Pendulum'
#Define an explicit solver
solver = CVode(pend_mod)
time = 10
t1,y1 = solver(time)
P.plot(y1[:,0],y1[:,1])
P.grid()
P.show()
P.title('CVode for k = 1, time = 30s')
P.xlabel('X-pos')
P.ylabel('Y-pos')