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make large rotation penalty optional in chpi function #8770

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Merged
larsoner merged 3 commits into from
Mar 2, 2021
Merged

make large rotation penalty optional in chpi function #8770

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b1e53e5
add option to penalized large rotations
bloyl Jan 20, 2021
6fbade5
Use Bias
bloyl Feb 26, 2021
c050561
Merge remote-tracking branch 'upstream/main' into chpi_ordering
larsoner Mar 1, 2021
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15 changes: 9 additions & 6 deletions mne/chpi.py
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Original file line number Diff line number Diff line change
Expand Up @@ -491,7 +491,7 @@ def _fit_chpi_quat(coil_dev_rrs, coil_head_rrs):
return quat, gof


def _fit_coil_order_dev_head_trans(dev_pnts, head_pnts):
def _fit_coil_order_dev_head_trans(dev_pnts, head_pnts, bias=True):
"""Compute Device to Head transform allowing for permutiatons of points."""
id_quat = np.zeros(6)
best_order = None
Expand All @@ -501,11 +501,14 @@ def _fit_coil_order_dev_head_trans(dev_pnts, head_pnts):
head_pnts_tmp = head_pnts[np.array(this_order)]
this_quat, g = _fit_chpi_quat(dev_pnts, head_pnts_tmp)
assert np.linalg.det(quat_to_rot(this_quat[:3])) > 0.9999
# For symmetrical arrangements, flips can produce roughly
# equivalent g values. To avoid this, heavily penalize
# large rotations.
rotation = _angle_between_quats(this_quat[:3], np.zeros(3))
check_g = g * max(1. - rotation / np.pi, 0) ** 0.25
if bias:
# For symmetrical arrangements, flips can produce roughly
# equivalent g values. To avoid this, heavily penalize
# large rotations.
rotation = _angle_between_quats(this_quat[:3], np.zeros(3))
check_g = g * max(1. - rotation / np.pi, 0) ** 0.25
else:
check_g = g
if check_g > best_g:
out_g = g
best_g = check_g
Expand Down