NaN issue

eph.py

import PyKEP
import random
import math

r_ang = random.uniform(0, math.pi * 2)
rx = math.cos(r_ang)
ry = math.sin(r_ang)
rz = 0

vx = -math.sin(r_ang)
vy = math.cos(r_ang)
vz = random.uniform(0, 1)

r = [rx, ry, rz] # mag = 1.0
v = [vx, vy, vz] # ~1.4 > mag > 1.0
mu = 1

s = PyKEP.planet.keplerian(PyKEP.epoch(0), r, v, mu, 0, 1, 2)

print 'Elements: %5.5f, %5.5f, %5.5f, %5.5f, %5.5f, %5.5f' % (s.orbital_elements)
print ' -> R(0): %3.3f, %3.3f, %3.3f' % (s.eph(PyKEP.epoch(0))[0])