def test_angle_axis():
for M, q in eg_pairs:
theta, vec = nq.quat2angle_axis(q)
q2 = nq.angle_axis2quat(theta, vec)
yield nq.nearly_equivalent, q, q2
aa_mat = nq.angle_axis2mat(theta, vec)
yield assert_array_almost_equal, aa_mat, M
def euler2angle_axis(z=0, y=0, x=0):
''' Return angle, axis corresponding to these Euler angles
Uses the z, then y, then x convention above
Parameters
----------
z : scalar
Rotation angle in radians around z-axis (performed first)
y : scalar
Rotation angle in radians around y-axis
x : scalar
Rotation angle in radians around x-axis (performed last)
Returns
-------
theta : scalar
angle of rotation
vector : array shape (3,)
axis around which rotation occurs
Examples
--------
>>> theta, vec = euler2angle_axis(0, 1.5, 0)
>>> theta
1.5
>>> np.allclose(vec, [0, 1, 0])
True
'''
# delayed import to avoid cyclic dependencies
import nipy.io.imageformats.quaternions as nq
return nq.quat2angle_axis(euler2quat(z, y, x))
