""" Testing diffusion parameter processing
"""
import numpy as np
from ..dwiparams import B2q
from nose.tools import assert_true, assert_false, \
assert_equal, assert_raises
from numpy.testing import assert_array_equal, assert_array_almost_equal
def test_b2q():
# conversion of b matrix to q
q = np.array([1,2,3])
s = np.sqrt(np.sum(q * q)) # vector norm
B = np.outer(q, q)
assert_array_almost_equal(q*s, B2q(B))
q = np.array([1,2,3])
# check that the sign of the vector as positive x convention
B = np.outer(-q, -q)
assert_array_almost_equal(q*s, B2q(B))
q = np.array([-1, 2, 3])
B = np.outer(q, q)
assert_array_almost_equal(-q*s, B2q(B))
B = np.eye(3) * -1
assert_raises(ValueError, B2q, B)
# no error if we up the tolerance
q = B2q(B, tol=1)
