def test_nnls_jacobian_fucn():
b0 = 1000.
bvecs, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table(bval, bvecs)
B = bval[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
# Design Matrix
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
# Test Jacobian at D
args = [X, Y]
analytical = dti._nlls_jacobian_func(D, *args)
for i in range(len(X)):
args = [X[i], Y[i]]
approx = opt.approx_fprime(D, dti._nlls_err_func, 1e-8, *args)
assert_true(np.allclose(approx, analytical[i]))
# Test Jacobian at zero
D = np.zeros_like(D)
args = [X, Y]
analytical = dti._nlls_jacobian_func(D, *args)
for i in range(len(X)):
args = [X[i], Y[i]]
approx = opt.approx_fprime(D, dti._nlls_err_func, 1e-8, *args)
assert_true(np.allclose(approx, analytical[i]))
def test_nnls_jacobian_fucn():
b0 = 1000.
bvecs, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table(bval, bvecs)
B = bval[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
# Design Matrix
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
# Test Jacobian at D
args = [X, Y]
analytical = dti._nlls_jacobian_func(D, *args)
for i in range(len(X)):
args = [X[i], Y[i]]
approx = opt.approx_fprime(D, dti._nlls_err_func, 1e-8, *args)
assert_true(np.allclose(approx, analytical[i]))
# Test Jacobian at zero
D = np.zeros_like(D)
args = [X, Y]
analytical = dti._nlls_jacobian_func(D, *args)
for i in range(len(X)):
args = [X[i], Y[i]]
approx = opt.approx_fprime(D, dti._nlls_err_func, 1e-8, *args)
assert_true(np.allclose(approx, analytical[i]))
def test_passing_maskedview():
data = np.ones((2, 4, 56))
mask = np.array([[True, False, False, True], [True, False, True, False]])
gtab, bval = read_bvec_file(get_data('55dir_grad.bvec'))
data = data[mask]
mv = MaskedView(mask, data)
tensor = dti.Tensor(mv, bval, gtab.T, min_signal=1e-9)
assert_equal(tensor.shape, (2, 4))
assert_equal(tensor.fa().shape, (2, 4))
assert_equal(tensor.evals.shape, (2, 4, 3))
assert_equal(tensor.evecs.shape, (2, 4, 3, 3))
assert_equal(type(tensor.model_params), MaskedView)
assert_array_equal(tensor.mask, mask)
tensor = tensor[0]
assert_equal(tensor.shape, (4, ))
assert_equal(tensor.fa().shape, (4, ))
assert_equal(tensor.evals.shape, (4, 3))
assert_equal(tensor.evecs.shape, (4, 3, 3))
assert_equal(type(tensor.model_params), MaskedView)
assert_array_equal(tensor.mask, mask[0])
tensor = tensor[0]
assert_equal(tensor.shape, tuple())
assert_equal(tensor.fa().shape, tuple())
assert_equal(tensor.evals.shape, (3, ))
assert_equal(tensor.evecs.shape, (3, 3))
assert_equal(type(tensor.model_params), np.ndarray)
def test_passing_maskedview():
data = np.ones((2,4,56))
mask = np.array([[True, False, False, True],
[True, False, True, False]])
gtab, bval = read_bvec_file(get_data('55dir_grad.bvec'))
data = data[mask]
mv = MaskedView(mask, data)
tensor = dti.Tensor(mv, bval, gtab.T, min_signal=1e-9)
assert_equal(tensor.shape, (2,4))
assert_equal(tensor.fa().shape, (2,4))
assert_equal(tensor.evals.shape, (2,4,3))
assert_equal(tensor.evecs.shape, (2,4,3,3))
assert_equal(type(tensor.model_params), MaskedView)
assert_array_equal(tensor.mask, mask)
tensor = tensor[0]
assert_equal(tensor.shape, (4,))
assert_equal(tensor.fa().shape, (4,))
assert_equal(tensor.evals.shape, (4,3))
assert_equal(tensor.evecs.shape, (4,3,3))
assert_equal(type(tensor.model_params), MaskedView)
assert_array_equal(tensor.mask, mask[0])
tensor = tensor[0]
assert_equal(tensor.shape, tuple())
assert_equal(tensor.fa().shape, tuple())
assert_equal(tensor.evals.shape, (3,))
assert_equal(tensor.evecs.shape, (3,3))
assert_equal(type(tensor.model_params), np.ndarray)
def test_all_zeros():
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
fit_methods = ['LS', 'OLS', 'NNLS', 'RESTORE']
for fit_method in fit_methods:
dm = dti.TensorModel(gtab)
assert_raises(ValueError, dm.fit, np.zeros(bvals.shape[0]))
def test_masked_array_with_Tensor():
data = np.ones((2,4,56))
mask = np.array([[True, False, False, True],
[True, False, True, False]])
gtab, bval = read_bvec_file(get_data('55dir_grad.bvec'))
tensor = dti.Tensor(data, bval, gtab.T, mask=mask, min_signal=1e-9)
yield assert_equal(tensor.shape, (2,4))
yield assert_equal(tensor.fa().shape, (2,4))
yield assert_equal(tensor.evals.shape, (2,4,3))
yield assert_equal(tensor.evecs.shape, (2,4,3,3))
yield assert_equal(type(tensor.model_params), MaskedView)
yield assert_array_equal(tensor.mask, mask)
tensor = tensor[0]
yield assert_equal(tensor.shape, (4,))
yield assert_equal(tensor.fa().shape, (4,))
yield assert_equal(tensor.evals.shape, (4,3))
yield assert_equal(tensor.evecs.shape, (4,3,3))
yield assert_equal(type(tensor.model_params), MaskedView)
yield assert_array_equal(tensor.mask, mask[0])
tensor = tensor[0]
yield assert_equal(tensor.shape, tuple())
yield assert_equal(tensor.fa().shape, tuple())
yield assert_equal(tensor.evals.shape, (3,))
yield assert_equal(tensor.evecs.shape, (3,3))
yield assert_equal(type(tensor.model_params), np.ndarray)
def test_all_zeros():
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
fit_methods = ['LS', 'OLS', 'NNLS', 'RESTORE']
for fit_method in fit_methods:
dm = dti.TensorModel(gtab)
assert_raises(ValueError, dm.fit, np.zeros(bvals.shape[0]))
def test_masked_array_with_tensor():
data = np.ones((2, 4, 56))
mask = np.array([[True, False, False, True],
[True, False, True, False]])
bvec, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bval, bvec.T)
tensor_model = TensorModel(gtab)
tensor = tensor_model.fit(data, mask=mask)
assert_equal(tensor.shape, (2, 4))
assert_equal(tensor.fa.shape, (2, 4))
assert_equal(tensor.evals.shape, (2, 4, 3))
assert_equal(tensor.evecs.shape, (2, 4, 3, 3))
tensor = tensor[0]
assert_equal(tensor.shape, (4,))
assert_equal(tensor.fa.shape, (4,))
assert_equal(tensor.evals.shape, (4, 3))
assert_equal(tensor.evecs.shape, (4, 3, 3))
tensor = tensor[0]
assert_equal(tensor.shape, tuple())
assert_equal(tensor.fa.shape, tuple())
assert_equal(tensor.evals.shape, (3,))
assert_equal(tensor.evecs.shape, (3, 3))
assert_equal(type(tensor.model_params), np.ndarray)
def test_all_zeros():
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
fit_methods = ['LS', 'OLS', 'NNLS', 'RESTORE']
for _ in fit_methods:
dm = dti.TensorModel(gtab)
assert_array_almost_equal(dm.fit(np.zeros(bvals.shape[0])).evals, 0)
def test_masked_array_with_tensor():
data = np.ones((2, 4, 56))
mask = np.array([[True, False, False, True],
[True, False, True, False]])
bvec, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bval, bvec.T)
tensor_model = TensorModel(gtab)
tensor = tensor_model.fit(data, mask=mask)
assert_equal(tensor.shape, (2, 4))
assert_equal(tensor.fa.shape, (2, 4))
assert_equal(tensor.evals.shape, (2, 4, 3))
assert_equal(tensor.evecs.shape, (2, 4, 3, 3))
tensor = tensor[0]
assert_equal(tensor.shape, (4,))
assert_equal(tensor.fa.shape, (4,))
assert_equal(tensor.evals.shape, (4, 3))
assert_equal(tensor.evecs.shape, (4, 3, 3))
tensor = tensor[0]
assert_equal(tensor.shape, tuple())
assert_equal(tensor.fa.shape, tuple())
assert_equal(tensor.evals.shape, (3,))
assert_equal(tensor.evecs.shape, (3, 3))
assert_equal(type(tensor.model_params), np.ndarray)
def test_restore():
"""
Test the implementation of the RESTORE algorithm
"""
b0 = 1000.
bvecs, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table(bval, bvecs)
B = bval[1]
#Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
#Design Matrix
X = dti.design_matrix(gtab)
#Signals
Y = np.exp(np.dot(X,D))
Y.shape = (-1,) + Y.shape
for drop_this in range(1, Y.shape[-1]):
# RESTORE estimates should be robust to dropping
this_y = Y.copy()
this_y[:, drop_this] = 1.0
tensor_model = dti.TensorModel(gtab, fit_method='restore',
sigma=67.0)
tensor_est = tensor_model.fit(this_y)
assert_array_almost_equal(tensor_est.evals[0], evals, decimal=3)
assert_array_almost_equal(tensor_est.quadratic_form[0], tensor,
decimal=3)
def test_all_zeros():
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
fit_methods = ['LS', 'OLS', 'NNLS', 'RESTORE']
for fit_method in fit_methods:
dm = dti.TensorModel(gtab)
assert_array_almost_equal(dm.fit(np.zeros(bvals.shape[0])).evals, 0)
def test_all_constant():
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
fit_methods = ['LS', 'OLS', 'NNLS']
for fit_method in fit_methods:
dm = dti.TensorModel(gtab)
assert_almost_equal(dm.fit(np.zeros(bvals.shape[0])).fa, 0)
assert_almost_equal(dm.fit(100 * np.ones(bvals.shape[0])).fa, 0)
def test_TensorModel():
data, gtab = dsi_voxels()
dm = dti.TensorModel(gtab, 'LS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.5, True)
dm = dti.TensorModel(gtab, 'WLS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.5, True)
sphere = create_unit_sphere(4)
assert_equal(len(dtifit.odf(sphere)), len(sphere.vertices))
assert_almost_equal(dtifit.fa, gfa(dtifit.odf(sphere)), 1)
# Check that the multivoxel case works:
dtifit = dm.fit(data)
assert_equal(dtifit.fa.shape, data.shape[:3])
# Make some synthetic data
b0 = 1000.
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
# The first b value is 0., so we take the second one:
B = bvals[1]
#Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
evecs = np.linalg.eigh(tensor)[1]
#Design Matrix
X = dti.design_matrix(bvecs, bvals)
#Signals
Y = np.exp(np.dot(X,D))
assert_almost_equal(Y[0], b0)
Y.shape = (-1,) + Y.shape
# Test fitting with different methods: #XXX Add NNLS methods!
for fit_method in ['OLS', 'WLS']:
tensor_model = dti.TensorModel(gtab,
fit_method=fit_method)
tensor_fit = tensor_model.fit(Y)
assert_true(tensor_fit.model is tensor_model)
assert_equal(tensor_fit.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_fit.evals[0], evals)
assert_array_almost_equal(tensor_fit.quadratic_form[0], tensor,
err_msg =\
"Calculation of tensor from Y does not compare to analytical solution")
assert_almost_equal(tensor_fit.md[0], md)
assert_equal(tensor_fit.directions.shape[-2], 1)
assert_equal(tensor_fit.directions.shape[-1], 3)
# Test error-handling:
assert_raises(ValueError,
dti.TensorModel,
gtab,
fit_method='crazy_method')
def test_WLS_and_LS_fit():
"""
Tests the WLS and LS fitting functions to see if they returns the correct
eigenvalues and eigenvectors.
Uses data/55dir_grad.bvec as the gradient table and 3by3by56.nii
as the data.
"""
### Defining Test Voxel (avoid nibabel dependency) ###
#Recall: D = [Dxx,Dyy,Dzz,Dxy,Dxz,Dyz,log(S_0)] and D ~ 10^-4 mm^2 /s
b0 = 1000.
bvec, bval = read_bvec_file(get_data('55dir_grad.bvec'))
B = bval[1]
#Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
#Design Matrix
X = dti.design_matrix(bvec, bval)
#Signals
Y = np.exp(np.dot(X, D))
assert_almost_equal(Y[0], b0)
Y.shape = (-1,) + Y.shape
gtab = grad.gradient_table(bval, bvec)
### Testing WLS Fit on Single Voxel ###
#Estimate tensor from test signals
model = TensorModel(gtab, min_signal=1e-8, fit_method='WLS')
tensor_est = model.fit(Y)
assert_equal(tensor_est.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_est.evals[0], evals)
assert_array_almost_equal(tensor_est.quadratic_form[0], tensor,
err_msg="Calculation of tensor from Y does not "
"compare to analytical solution")
assert_almost_equal(tensor_est.md[0], md)
# Test that we can fit a single voxel's worth of data (a 1d array)
y = Y[0]
tensor_est = model.fit(y)
assert_equal(tensor_est.shape, tuple())
assert_array_almost_equal(tensor_est.evals, evals)
assert_array_almost_equal(tensor_est.quadratic_form, tensor)
assert_almost_equal(tensor_est.md, md)
assert_array_almost_equal(tensor_est.lower_triangular(b0), D)
# Test using fit_method='LS'
model = TensorModel(gtab, min_signal=1e-8, fit_method='LS')
tensor_est = model.fit(y)
assert_equal(tensor_est.shape, tuple())
assert_array_almost_equal(tensor_est.evals, evals)
assert_array_almost_equal(tensor_est.quadratic_form, tensor)
assert_almost_equal(tensor_est.md, md)
assert_array_almost_equal(tensor_est.lower_triangular(b0), D)
def test_all_constant():
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
fit_methods = ['LS', 'OLS', 'NNLS', 'RESTORE']
for fit_method in fit_methods:
dm = dti.TensorModel(gtab)
assert_almost_equal(dm.fit(100 * np.ones(bvals.shape[0])).fa, 0)
# Doesn't matter if the signal is smaller than 1:
assert_almost_equal(dm.fit(0.4 * np.ones(bvals.shape[0])).fa, 0)
def test_all_constant():
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
fit_methods = ['LS', 'OLS', 'NNLS', 'RESTORE']
for _ in fit_methods:
dm = dti.TensorModel(gtab)
assert_almost_equal(dm.fit(100 * np.ones(bvals.shape[0])).fa, 0)
# Doesn't matter if the signal is smaller than 1:
assert_almost_equal(dm.fit(0.4 * np.ones(bvals.shape[0])).fa, 0)
def test_fit_method_error():
bvec, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bval, bvec.T)
# This should work (smoke-testing!):
TensorModel(gtab, fit_method='WLS')
# This should raise an error because there is no such fit_method
assert_raises(ValueError, TensorModel, gtab, min_signal=1e-9,
fit_method='s')
def test_fit_method_error():
bvec, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bval, bvec.T)
# This should work (smoke-testing!):
TensorModel(gtab, fit_method='WLS')
# This should raise an error because there is no such fit_method
assert_raises(ValueError, TensorModel, gtab, min_signal=1e-9,
fit_method='s')
def test_WLS_and_LS_fit():
"""
Tests the WLS and LS fitting functions to see if they returns the correct
eigenvalues and eigenvectors.
Uses data/55dir_grad.bvec as the gradient table and 3by3by56.nii
as the data.
"""
### Defining Test Voxel (avoid nibabel dependency) ###
#Recall: D = [Dxx,Dyy,Dzz,Dxy,Dxz,Dyz,log(S_0)] and D ~ 10^-4 mm^2 /s
b0 = 1000.
gtab, bval = read_bvec_file(get_data('55dir_grad.bvec'))
B = bval[1]
#Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
#Design Matrix
X = dti.design_matrix(gtab, bval)
#Signals
Y = np.exp(np.dot(X, D))
assert_almost_equal(Y[0], b0)
Y.shape = (-1, ) + Y.shape
### Testing WLS Fit on Single Voxel ###
#Estimate tensor from test signals
tensor_est = dti.Tensor(Y, bval, gtab.T, min_signal=1e-8)
assert_equal(tensor_est.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_est.evals[0], evals)
assert_array_almost_equal(
tensor_est.D[0],
tensor,
err_msg=
"Calculation of tensor from Y does not compare to analytical solution")
assert_almost_equal(tensor_est.md()[0], md)
#test 0d tensor
y = Y[0]
tensor_est = dti.Tensor(y, bval, gtab.T, min_signal=1e-8)
assert_equal(tensor_est.shape, tuple())
assert_array_almost_equal(tensor_est.evals, evals)
assert_array_almost_equal(tensor_est.D, tensor)
assert_almost_equal(tensor_est.md(), md)
assert_array_almost_equal(tensor_est.lower_triangular(b0), D)
tensor_est = dti.Tensor(y, bval, gtab.T, min_signal=1e-8, fit_method='LS')
assert_equal(tensor_est.shape, tuple())
assert_array_almost_equal(tensor_est.evals, evals)
assert_array_almost_equal(tensor_est.D, tensor)
assert_almost_equal(tensor_est.md(), md)
assert_array_almost_equal(tensor_est.lower_triangular(b0), D)
def test_all_constant():
"""
"""
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
fit_methods = ['LS', 'OLS', 'NNLS']
for fit_method in fit_methods:
dm = dti.TensorModel(gtab)
assert_almost_equal(dm.fit(np.zeros(bvals.shape[0])).fa, 0)
assert_almost_equal(dm.fit(100 * np.ones(bvals.shape[0])).fa, 0)
def test_init():
data = np.ones((2, 4, 56))
mask = np.ones((2, 4), 'bool')
gtab, bval = read_bvec_file(get_data('55dir_grad.bvec'))
tensor = dti.Tensor(data, bval, gtab.T, mask, thresh=0)
mask[:] = False
assert_raises(ValueError, dti.Tensor, data, bval, gtab.T, mask)
assert_raises(ValueError, dti.Tensor, data, bval, gtab.T, min_signal=-1)
assert_raises(ValueError, dti.Tensor, data, bval, gtab.T, thresh=1)
assert_raises(ValueError, dti.Tensor, data, bval, gtab.T, fit_method='s')
assert_raises(ValueError, dti.Tensor, data, bval, gtab.T, fit_method=0)
def test_WLS_and_LS_fit():
"""
Tests the WLS and LS fitting functions to see if they returns the correct
eigenvalues and eigenvectors.
Uses data/55dir_grad.bvec as the gradient table and 3by3by56.nii
as the data.
"""
### Defining Test Voxel (avoid nibabel dependency) ###
#Recall: D = [Dxx,Dyy,Dzz,Dxy,Dxz,Dyz,log(S_0)] and D ~ 10^-4 mm^2 /s
D = np.array([1., 1., 1., 1., 0., 0., np.log(1000) * 10.**4]) * 10.**-4
evals = np.array([2., 1., 0.]) * 10.**-4
md = evals.mean()
tensor = np.empty((3,3))
tensor[0, 0] = D[0]
tensor[1, 1] = D[1]
tensor[2, 2] = D[2]
tensor[0, 1] = tensor[1, 0] = D[3]
tensor[0, 2] = tensor[2, 0] = D[4]
tensor[1, 2] = tensor[2, 1] = D[5]
#Design Matrix
gtab, bval = read_bvec_file(get_data('55dir_grad.bvec'))
X = dti.design_matrix(gtab, bval)
#Signals
Y = np.exp(np.dot(X,D))
Y.shape = (-1,) + Y.shape
### Testing WLS Fit on Single Voxel ###
#Estimate tensor from test signals
tensor_est = dti.Tensor(Y,bval,gtab.T,min_signal=1e-8)
yield assert_equal(tensor_est.shape, Y.shape[:-1])
yield assert_array_almost_equal(tensor_est.evals[0], evals)
yield assert_array_almost_equal(tensor_est.D[0], tensor,err_msg= "Calculation of tensor from Y does not compare to analytical solution")
yield assert_almost_equal(tensor_est.md()[0], md)
#test 0d tensor
y = Y[0]
tensor_est = dti.Tensor(y, bval, gtab.T, min_signal=1e-8)
yield assert_equal(tensor_est.shape, tuple())
yield assert_array_almost_equal(tensor_est.evals, evals)
yield assert_array_almost_equal(tensor_est.D, tensor)
yield assert_almost_equal(tensor_est.md(), md)
tensor_est = dti.Tensor(y, bval, gtab.T, min_signal=1e-8, fit_method='LS')
yield assert_equal(tensor_est.shape, tuple())
yield assert_array_almost_equal(tensor_est.evals, evals)
yield assert_array_almost_equal(tensor_est.D, tensor)
yield assert_almost_equal(tensor_est.md(), md)
def test_restore():
"""
Test the implementation of the RESTORE algorithm
"""
b0 = 1000.
bvecs, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table(bval, bvecs)
B = bval[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
tensor = from_lower_triangular(D)
# Design Matrix
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
Y.shape = (-1, ) + Y.shape
for drop_this in range(1, Y.shape[-1]):
for jac in [True, False]:
# RESTORE estimates should be robust to dropping
this_y = Y.copy()
this_y[:, drop_this] = 1.0
for sigma in [67.0, np.ones(this_y.shape[-1]) * 67.0]:
tensor_model = dti.TensorModel(gtab,
fit_method='restore',
jac=jac,
sigma=67.0)
tensor_est = tensor_model.fit(this_y)
assert_array_almost_equal(tensor_est.evals[0],
evals,
decimal=3)
assert_array_almost_equal(tensor_est.quadratic_form[0],
tensor,
decimal=3)
# If sigma is very small, it still needs to work:
tensor_model = dti.TensorModel(gtab, fit_method='restore', sigma=0.0001)
tensor_model.fit(Y.copy())
# Test return_S0_hat
tensor_model = dti.TensorModel(gtab,
fit_method='restore',
sigma=0.0001,
return_S0_hat=True)
tmf = tensor_model.fit(Y.copy())
assert_almost_equal(tmf[0].S0_hat, b0)
def test_nlls_fit_tensor():
"""
Test the implementation of NLLS and RESTORE
"""
b0 = 1000.
bvecs, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table(bval, bvecs)
B = bval[1]
#Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
#Design Matrix
X = dti.design_matrix(bvecs, bval)
#Signals
Y = np.exp(np.dot(X,D))
Y.shape = (-1,) + Y.shape
#Estimate tensor from test signals and compare against expected result
#using non-linear least squares:
tensor_model = dti.TensorModel(gtab, fit_method='NLLS')
tensor_est = tensor_model.fit(Y)
assert_equal(tensor_est.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_est.evals[0], evals)
assert_array_almost_equal(tensor_est.quadratic_form[0], tensor)
assert_almost_equal(tensor_est.md[0], md)
# Using the gmm weighting scheme:
tensor_model = dti.TensorModel(gtab, fit_method='NLLS', weighting='gmm')
assert_equal(tensor_est.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_est.evals[0], evals)
assert_array_almost_equal(tensor_est.quadratic_form[0], tensor)
assert_almost_equal(tensor_est.md[0], md)
# Use NLLS with some actual 4D data:
data, bvals, bvecs = get_data('small_25')
gtab = grad.gradient_table(bvals, bvecs)
tm1 = dti.TensorModel(gtab, fit_method='NLLS')
dd = nib.load(data).get_data()
tf1 = tm1.fit(dd)
tm2 = dti.TensorModel(gtab)
tf2 = tm2.fit(dd)
assert_array_almost_equal(tf1.fa, tf2.fa, decimal=1)
def test_nlls_fit_tensor():
"""
Test the implementation of NLLS and RESTORE
"""
b0 = 1000.
bvecs, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table(bval, bvecs)
B = bval[1]
#Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
#Design Matrix
X = dti.design_matrix(bvecs, bval)
#Signals
Y = np.exp(np.dot(X,D))
Y.shape = (-1,) + Y.shape
#Estimate tensor from test signals and compare against expected result
#using non-linear least squares:
tensor_model = dti.TensorModel(gtab, fit_method='NLLS')
tensor_est = tensor_model.fit(Y)
assert_equal(tensor_est.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_est.evals[0], evals)
assert_array_almost_equal(tensor_est.quadratic_form[0], tensor)
assert_almost_equal(tensor_est.md[0], md)
# Using the gmm weighting scheme:
tensor_model = dti.TensorModel(gtab, fit_method='NLLS', weighting='gmm')
assert_equal(tensor_est.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_est.evals[0], evals)
assert_array_almost_equal(tensor_est.quadratic_form[0], tensor)
assert_almost_equal(tensor_est.md[0], md)
# Use NLLS with some actual 4D data:
data, bvals, bvecs = get_data('small_25')
gtab = grad.gradient_table(bvals, bvecs)
tm1 = dti.TensorModel(gtab, fit_method='NLLS')
dd = nib.load(data).get_data()
tf1 = tm1.fit(dd)
tm2 = dti.TensorModel(gtab)
tf2 = tm2.fit(dd)
assert_array_almost_equal(tf1.fa, tf2.fa, decimal=1)
def test_init():
data = np.ones((2,4,56))
mask = np.ones((2,4),'bool')
gtab, bval = read_bvec_file(get_data('55dir_grad.bvec'))
tensor = dti.Tensor(data, bval, gtab.T, mask, thresh=0)
mask[:] = False
assert_raises(ValueError, dti.Tensor, data, bval, gtab.T, mask)
assert_raises(ValueError, dti.Tensor, data, bval, gtab.T,
min_signal=-1)
assert_raises(ValueError, dti.Tensor, data, bval, gtab.T, thresh=1)
assert_raises(ValueError, dti.Tensor, data, bval, gtab.T,
fit_method='s')
assert_raises(ValueError, dti.Tensor, data, bval, gtab.T,
fit_method=0)
def sample_hardi_data():
"""High Angular Resulution Diffusion Imaging data with 150 diffusion
directions
"""
data_img = load(pjoin(THIS_DIR, 'E1381S6_edcor.nii.gz'))
data = data_img.get_data()
aff = data_img.get_affine()
data_hdr = data_img.get_header()
voxel_size = data_hdr.get_zooms()
voxel_size = voxel_size[:3]
fa_img = load(pjoin(THIS_DIR, 'E1381S6_edcor_fa.nii.gz'))
fa = fa_img.get_data()
bvec, bval = read_bvec_file(pjoin(THIS_DIR, 'E1381S6_edcor.bval'))
return data, fa, bvec, bval, voxel_size
def sample_hardi_data():
"""High Angular Resulution Diffusion Imaging data with 150 diffusion
directions
"""
data_img = load(pjoin(THIS_DIR, 'E1381S6_edcor.nii.gz'))
data = data_img.get_data()
aff = data_img.get_affine()
data_hdr = data_img.get_header()
voxel_size = data_hdr.get_zooms()
voxel_size = voxel_size[:3]
fa_img = load(pjoin(THIS_DIR, 'E1381S6_edcor_fa.nii.gz'))
fa = fa_img.get_data()
bvec, bval = read_bvec_file(pjoin(THIS_DIR, 'E1381S6_edcor.bval'))
return data, fa, bvec, bval, voxel_size
def test_restore():
"""
Test the implementation of the RESTORE algorithm
"""
b0 = 1000.
bvecs, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table(bval, bvecs)
B = bval[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
tensor = from_lower_triangular(D)
# Design Matrix
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
Y.shape = (-1,) + Y.shape
for drop_this in range(1, Y.shape[-1]):
for jac in [True, False]:
# RESTORE estimates should be robust to dropping
this_y = Y.copy()
this_y[:, drop_this] = 1.0
for _ in [67.0, np.ones(this_y.shape[-1]) * 67.0]:
tensor_model = dti.TensorModel(gtab, fit_method='restore',
jac=jac,
sigma=67.0)
tensor_est = tensor_model.fit(this_y)
assert_array_almost_equal(tensor_est.evals[0], evals,
decimal=3)
assert_array_almost_equal(tensor_est.quadratic_form[0], tensor,
decimal=3)
# If sigma is very small, it still needs to work:
tensor_model = dti.TensorModel(gtab, fit_method='restore', sigma=0.0001)
tensor_model.fit(Y.copy())
# Test return_S0_hat
tensor_model = dti.TensorModel(gtab, fit_method='restore', sigma=0.0001,
return_S0_hat=True)
tmf = tensor_model.fit(Y.copy())
assert_almost_equal(tmf[0].S0_hat, b0)
def test_restore():
"""
Test the implementation of the RESTORE algorithm
"""
b0 = 1000.
bvecs, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table(bval, bvecs)
B = bval[1]
#Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
#Design Matrix
X = dti.design_matrix(bvecs, bval)
#Signals
Y = np.exp(np.dot(X,D))
Y.shape = (-1,) + Y.shape
for sigma in [0.1, 1, 10, 100]:
for drop_this in range(1, Y.shape[-1]):
# RESTORE estimates should be robust to dropping
this_y = Y.copy()
this_y[:, drop_this] = 1.0
tensor_model = dti.TensorModel(gtab, fit_method='restore',
sigma=sigma)
tensor_est = tensor_model.fit(Y)
assert_array_almost_equal(tensor_est.evals[0], evals)
assert_array_almost_equal(tensor_est.quadratic_form[0], tensor)
data, bvals, bvecs = get_data('small_25')
dd = nib.load(data).get_data()
gtab = grad.gradient_table(bvals, bvecs)
fit_method = 'restore' # 'NLLS'
jac = True # False
dd[..., 5] = 1.0
tm = dti.TensorModel(gtab, fit_method=fit_method, jac=True, sigma=10)
tm.fit(dd)
def test_restore():
"""
Test the implementation of the RESTORE algorithm
"""
b0 = 1000.
bvecs, bval = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table(bval, bvecs)
B = bval[1]
#Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
#Design Matrix
X = dti.design_matrix(bvecs, bval)
#Signals
Y = np.exp(np.dot(X,D))
Y.shape = (-1,) + Y.shape
for sigma in [0.1, 1, 10, 100]:
for drop_this in range(1, Y.shape[-1]):
# RESTORE estimates should be robust to dropping
this_y = Y.copy()
this_y[:, drop_this] = 1.0
tensor_model = dti.TensorModel(gtab, fit_method='restore',
sigma=sigma)
tensor_est = tensor_model.fit(Y)
assert_array_almost_equal(tensor_est.evals[0], evals)
assert_array_almost_equal(tensor_est.quadratic_form[0], tensor)
data, bvals, bvecs = get_data('small_25')
dd = nib.load(data).get_data()
gtab = grad.gradient_table(bvals, bvecs)
fit_method = 'restore' # 'NLLS'
jac = True # False
dd[..., 5] = 1.0
tm = dti.TensorModel(gtab, fit_method=fit_method, jac=True, sigma=10)
tm.fit(dd)
def test_nlls_fit_tensor():
"""
Test the implementation of NLLS and RESTORE
"""
b0 = 1000.
bvecs, bval = read_bvec_file(get_fnames('55dir_grad.bvec'))
gtab = grad.gradient_table(bval, bvecs)
B = bval[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
# Design Matrix
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
Y.shape = (-1, ) + Y.shape
# Estimate tensor from test signals and compare against expected result
# using non-linear least squares:
tensor_model = dti.TensorModel(gtab, fit_method='NLLS')
tensor_est = tensor_model.fit(Y)
npt.assert_equal(tensor_est.shape, Y.shape[:-1])
npt.assert_array_almost_equal(tensor_est.evals[0], evals)
npt.assert_array_almost_equal(tensor_est.quadratic_form[0], tensor)
npt.assert_almost_equal(tensor_est.md[0], md)
# You can also do this without the Jacobian (though it's slower):
tensor_model = dti.TensorModel(gtab, fit_method='NLLS', jac=False)
tensor_est = tensor_model.fit(Y)
npt.assert_equal(tensor_est.shape, Y.shape[:-1])
npt.assert_array_almost_equal(tensor_est.evals[0], evals)
npt.assert_array_almost_equal(tensor_est.quadratic_form[0], tensor)
npt.assert_almost_equal(tensor_est.md[0], md)
# Using the gmm weighting scheme:
tensor_model = dti.TensorModel(gtab, fit_method='NLLS', weighting='gmm')
tensor_est = tensor_model.fit(Y)
npt.assert_equal(tensor_est.shape, Y.shape[:-1])
npt.assert_array_almost_equal(tensor_est.evals[0], evals)
npt.assert_array_almost_equal(tensor_est.quadratic_form[0], tensor)
npt.assert_almost_equal(tensor_est.md[0], md)
# If you use sigma weighting, you'd better provide a sigma:
tensor_model = dti.TensorModel(gtab, fit_method='NLLS', weighting='sigma')
npt.assert_raises(ValueError, tensor_model.fit, Y)
# Use NLLS with some actual 4D data:
data, bvals, bvecs = get_fnames('small_25')
gtab = grad.gradient_table(bvals, bvecs)
tm1 = dti.TensorModel(gtab, fit_method='NLLS')
dd = load_nifti_data(data)
tf1 = tm1.fit(dd)
tm2 = dti.TensorModel(gtab)
tf2 = tm2.fit(dd)
npt.assert_array_almost_equal(tf1.fa, tf2.fa, decimal=1)
def test_wls_and_ls_fit():
"""
Tests the WLS and LS fitting functions to see if they returns the correct
eigenvalues and eigenvectors.
Uses data/55dir_grad.bvec as the gradient table and 3by3by56.nii
as the data.
"""
# Defining Test Voxel (avoid nibabel dependency) ###
# Recall: D = [Dxx,Dyy,Dzz,Dxy,Dxz,Dyz,log(S_0)] and D ~ 10^-4 mm^2 /s
b0 = 1000.
bvec, bval = read_bvec_file(get_fnames('55dir_grad.bvec'))
B = bval[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
# Design Matrix
gtab = grad.gradient_table(bval, bvec)
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
npt.assert_almost_equal(Y[0], b0)
Y.shape = (-1,) + Y.shape
# Testing WLS Fit on Single Voxel
# If you do something wonky (passing min_signal<0), you should get an
# error:
npt.assert_raises(ValueError, TensorModel, gtab, fit_method='WLS',
min_signal=-1)
# Estimate tensor from test signals
model = TensorModel(gtab, fit_method='WLS', return_S0_hat=True)
tensor_est = model.fit(Y)
npt.assert_equal(tensor_est.shape, Y.shape[:-1])
npt.assert_array_almost_equal(tensor_est.evals[0], evals)
npt.assert_array_almost_equal(tensor_est.quadratic_form[0], tensor,
err_msg="Calculation of tensor from Y does "
"not compare to analytical solution")
npt.assert_almost_equal(tensor_est.md[0], md)
npt.assert_array_almost_equal(tensor_est.S0_hat[0], b0, decimal=3)
# Test that we can fit a single voxel's worth of data (a 1d array)
y = Y[0]
tensor_est = model.fit(y)
npt.assert_equal(tensor_est.shape, tuple())
npt.assert_array_almost_equal(tensor_est.evals, evals)
npt.assert_array_almost_equal(tensor_est.quadratic_form, tensor)
npt.assert_almost_equal(tensor_est.md, md)
npt.assert_array_almost_equal(tensor_est.lower_triangular(b0), D)
# Test using fit_method='LS'
model = TensorModel(gtab, fit_method='LS')
tensor_est = model.fit(y)
npt.assert_equal(tensor_est.shape, tuple())
npt.assert_array_almost_equal(tensor_est.evals, evals)
npt.assert_array_almost_equal(tensor_est.quadratic_form, tensor)
npt.assert_almost_equal(tensor_est.md, md)
npt.assert_array_almost_equal(tensor_est.lower_triangular(b0), D)
npt.assert_array_almost_equal(tensor_est.linearity, linearity(evals))
npt.assert_array_almost_equal(tensor_est.planarity, planarity(evals))
npt.assert_array_almost_equal(tensor_est.sphericity, sphericity(evals))
elif len(shape) < 3:
d = [1, 1, 1]
d[0:len(shape)] = shape
else:
d = shape
return np.mgrid[0:d[0], 0:d[1], 0:d[2]]
if __name__ == '__main__':
import dipy.core.qball as qball
from dipy.io.bvectxt import read_bvec_file
filename='/Users/bagrata/HARDI/E1322S8I1.nii.gz'
grad_table_filename='/Users/bagrata/HARDI/E1322S8I1.bvec'
from nipy import load_image, save_image
grad_table, b_values = read_bvec_file(grad_table_filename)
img = load_image(filename)
print 'input dimensions: '
print img.ndim
print 'image size: '
print img.shape
print 'image affine: '
print img.affine
print 'images has pixels with size: '
print np.dot(img.affine, np.eye(img.ndim+1)).diagonal()[0:3]
data = np.asarray(img)
theta, phi = np.mgrid[0:2*np.pi:64*1j, 0:np.pi:32*1j]
odf_i = qball.ODF(data[188:192,188:192,22:24,:],4,grad_table,b_values)
disp_odf(odf_i[0:1,0:2,0:2])
def test_tensor_model():
fdata, fbval, fbvec = get_data('small_25')
data1 = nib.load(fdata).get_data()
gtab1 = grad.gradient_table(fbval, fbvec)
data2, gtab2 = dsi_voxels()
for data, gtab in zip([data1, data2], [gtab1, gtab2]):
dm = dti.TensorModel(gtab, 'LS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.9, True)
dm = dti.TensorModel(gtab, 'WLS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.9, True)
assert_equal(dtifit.fa > 0, True)
sphere = create_unit_sphere(4)
assert_equal(len(dtifit.odf(sphere)), len(sphere.vertices))
# Check that the multivoxel case works:
dtifit = dm.fit(data)
# Check that it works on signal that has already been normalized to S0:
dm_to_relative = dti.TensorModel(gtab)
if np.any(gtab.b0s_mask):
relative_data = (data[0, 0, 0] /
np.mean(data[0, 0, 0, gtab.b0s_mask]))
dtifit_to_relative = dm_to_relative.fit(relative_data)
npt.assert_almost_equal(dtifit.fa[0, 0, 0],
dtifit_to_relative.fa,
decimal=3)
# And smoke-test that all these operations return sensibly-shaped arrays:
assert_equal(dtifit.fa.shape, data.shape[:3])
assert_equal(dtifit.ad.shape, data.shape[:3])
assert_equal(dtifit.md.shape, data.shape[:3])
assert_equal(dtifit.rd.shape, data.shape[:3])
assert_equal(dtifit.trace.shape, data.shape[:3])
assert_equal(dtifit.mode.shape, data.shape[:3])
assert_equal(dtifit.linearity.shape, data.shape[:3])
assert_equal(dtifit.planarity.shape, data.shape[:3])
assert_equal(dtifit.sphericity.shape, data.shape[:3])
# Test for the shape of the mask
assert_raises(ValueError, dm.fit, np.ones((10, 10, 3)), np.ones((3, 3)))
# Make some synthetic data
b0 = 1000.
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
# The first b value is 0., so we take the second one:
B = bvals[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
A_squiggle = tensor - (1 / 3.0) * np.trace(tensor) * np.eye(3)
mode = 3 * np.sqrt(6) * np.linalg.det(
A_squiggle / np.linalg.norm(A_squiggle))
evecs = np.linalg.eigh(tensor)[1]
# Design Matrix
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
assert_almost_equal(Y[0], b0)
Y.shape = (-1, ) + Y.shape
# Test fitting with different methods:
for fit_method in ['OLS', 'WLS', 'NLLS']:
tensor_model = dti.TensorModel(gtab, fit_method=fit_method)
tensor_fit = tensor_model.fit(Y)
assert_true(tensor_fit.model is tensor_model)
assert_equal(tensor_fit.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_fit.evals[0], evals)
assert_array_almost_equal(tensor_fit.quadratic_form[0], tensor,
err_msg=\
"Calculation of tensor from Y does not compare to analytical solution")
assert_almost_equal(tensor_fit.md[0], md)
assert_array_almost_equal(tensor_fit.mode, mode, decimal=5)
assert_equal(tensor_fit.directions.shape[-2], 1)
assert_equal(tensor_fit.directions.shape[-1], 3)
# Test error-handling:
assert_raises(ValueError, dti.TensorModel, gtab, fit_method='crazy_method')
# Test multi-voxel data
data = np.zeros((3, Y.shape[1]))
# Normal voxel
data[0] = Y
# High diffusion voxel, all diffusing weighted signal equal to zero
data[1, gtab.b0s_mask] = b0
data[1, ~gtab.b0s_mask] = 0
# Masked voxel, all data set to zero
data[2] = 0.
tensor_model = dti.TensorModel(gtab)
fit = tensor_model.fit(data)
assert_array_almost_equal(fit[0].evals, evals)
# Evals should be high for high diffusion voxel
assert_(all(fit[1].evals > evals[0] * .9))
# Evals should be zero where data is masked
assert_array_almost_equal(fit[2].evals, 0.)
def test_tensor_model():
fdata, fbval, fbvec = get_data('small_25')
data1 = nib.load(fdata).get_data()
gtab1 = grad.gradient_table(fbval, fbvec)
data2, gtab2 = dsi_voxels()
for data, gtab in zip([data1, data2], [gtab1, gtab2]):
dm = dti.TensorModel(gtab, 'LS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.9, True)
dm = dti.TensorModel(gtab, 'WLS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.9, True)
assert_equal(dtifit.fa > 0, True)
sphere = create_unit_sphere(4)
assert_equal(len(dtifit.odf(sphere)), len(sphere.vertices))
# Check that the multivoxel case works:
dtifit = dm.fit(data)
# Check that it works on signal that has already been normalized to S0:
dm_to_relative = dti.TensorModel(gtab)
if np.any(gtab.b0s_mask):
relative_data = (data[0, 0, 0]/np.mean(data[0, 0, 0,
gtab.b0s_mask]))
dtifit_to_relative = dm_to_relative.fit(relative_data)
npt.assert_almost_equal(dtifit.fa[0, 0, 0], dtifit_to_relative.fa,
decimal=3)
# And smoke-test that all these operations return sensibly-shaped arrays:
assert_equal(dtifit.fa.shape, data.shape[:3])
assert_equal(dtifit.ad.shape, data.shape[:3])
assert_equal(dtifit.md.shape, data.shape[:3])
assert_equal(dtifit.rd.shape, data.shape[:3])
assert_equal(dtifit.trace.shape, data.shape[:3])
assert_equal(dtifit.mode.shape, data.shape[:3])
assert_equal(dtifit.linearity.shape, data.shape[:3])
assert_equal(dtifit.planarity.shape, data.shape[:3])
assert_equal(dtifit.sphericity.shape, data.shape[:3])
# Test for the shape of the mask
assert_raises(ValueError, dm.fit, np.ones((10, 10, 3)), np.ones((3, 3)))
# Make some synthetic data
b0 = 1000.
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
# The first b value is 0., so we take the second one:
B = bvals[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
A_squiggle = tensor - (1 / 3.0) * np.trace(tensor) * np.eye(3)
mode = (3 * np.sqrt(6) * np.linalg.det(A_squiggle /
np.linalg.norm(A_squiggle)))
evals_eigh, evecs_eigh = np.linalg.eigh(tensor)
# Sort according to eigen-value from large to small:
evecs = evecs_eigh[:, np.argsort(evals_eigh)[::-1]]
# Check that eigenvalues and eigenvectors are properly sorted through
# that previous operation:
for i in range(3):
assert_array_almost_equal(np.dot(tensor, evecs[:, i]),
evals[i] * evecs[:, i])
# Design Matrix
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
assert_almost_equal(Y[0], b0)
Y.shape = (-1,) + Y.shape
# Test fitting with different methods:
for fit_method in ['OLS', 'WLS', 'NLLS']:
tensor_model = dti.TensorModel(gtab,
fit_method=fit_method,
return_S0_hat=True)
tensor_fit = tensor_model.fit(Y)
assert_true(tensor_fit.model is tensor_model)
assert_equal(tensor_fit.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_fit.evals[0], evals)
assert_array_almost_equal(tensor_fit.S0_hat, b0, decimal=3)
# Test that the eigenvectors are correct, one-by-one:
for i in range(3):
# Eigenvectors have intrinsic sign ambiguity
# (see
# http://prod.sandia.gov/techlib/access-control.cgi/2007/076422.pdf)
# so we need to allow for sign flips. One of the following should
# always be true:
assert_(
np.all(np.abs(tensor_fit.evecs[0][:, i] -
evecs[:, i]) < 10e-6) or
np.all(np.abs(-tensor_fit.evecs[0][:, i] -
evecs[:, i]) < 10e-6))
# We set a fixed tolerance of 10e-6, similar to array_almost_equal
err_msg = "Calculation of tensor from Y does not compare to "
err_msg += "analytical solution"
assert_array_almost_equal(tensor_fit.quadratic_form[0], tensor,
err_msg=err_msg)
assert_almost_equal(tensor_fit.md[0], md)
assert_array_almost_equal(tensor_fit.mode, mode, decimal=5)
assert_equal(tensor_fit.directions.shape[-2], 1)
assert_equal(tensor_fit.directions.shape[-1], 3)
# Test error-handling:
assert_raises(ValueError,
dti.TensorModel,
gtab,
fit_method='crazy_method')
# Test custom fit tensor method
try:
model = dti.TensorModel(gtab, fit_method=lambda *args, **kwargs: 42)
fit = model.fit_method()
except Exception as exc:
assert False, "TensorModel should accept custom fit methods: %s" % exc
assert fit == 42, "Custom fit method for TensorModel returned %s." % fit
# Test multi-voxel data
data = np.zeros((3, Y.shape[1]))
# Normal voxel
data[0] = Y
# High diffusion voxel, all diffusing weighted signal equal to zero
data[1, gtab.b0s_mask] = b0
data[1, ~gtab.b0s_mask] = 0
# Masked voxel, all data set to zero
data[2] = 0.
tensor_model = dti.TensorModel(gtab)
fit = tensor_model.fit(data)
assert_array_almost_equal(fit[0].evals, evals)
# Return S0_test
tensor_model = dti.TensorModel(gtab, return_S0_hat=True)
fit = tensor_model.fit(data)
assert_array_almost_equal(fit[0].evals, evals)
assert_array_almost_equal(fit[0].S0_hat, b0)
# Evals should be high for high diffusion voxel
assert_(all(fit[1].evals > evals[0] * .9))
# Evals should be zero where data is masked
assert_array_almost_equal(fit[2].evals, 0.)
def test_TensorModel():
data, gtab = dsi_voxels()
dm = dti.TensorModel(gtab, 'LS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.5, True)
dm = dti.TensorModel(gtab, 'WLS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.5, True)
sphere = create_unit_sphere(4)
assert_equal(len(dtifit.odf(sphere)), len(sphere.vertices))
assert_almost_equal(dtifit.fa, gfa(dtifit.odf(sphere)), 1)
# Check that the multivoxel case works:
dtifit = dm.fit(data)
# And smoke-test that all these operations return sensibly-shaped arrays:
assert_equal(dtifit.fa.shape, data.shape[:3])
assert_equal(dtifit.ad.shape, data.shape[:3])
assert_equal(dtifit.md.shape, data.shape[:3])
assert_equal(dtifit.rd.shape, data.shape[:3])
assert_equal(dtifit.trace.shape, data.shape[:3])
assert_equal(dtifit.mode.shape, data.shape[:3])
assert_equal(dtifit.linearity.shape, data.shape[:3])
assert_equal(dtifit.planarity.shape, data.shape[:3])
assert_equal(dtifit.sphericity.shape, data.shape[:3])
# Test for the shape of the mask
assert_raises(ValueError, dm.fit, np.ones((10, 10, 3)), np.ones((3,3)))
# Make some synthetic data
b0 = 1000.
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
# The first b value is 0., so we take the second one:
B = bvals[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
A_squiggle = tensor - (1 / 3.0) * np.trace(tensor) * np.eye(3)
mode = 3 * np.sqrt(6) * np.linalg.det(A_squiggle / np.linalg.norm(A_squiggle))
evecs = np.linalg.eigh(tensor)[1]
# Design Matrix
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
assert_almost_equal(Y[0], b0)
Y.shape = (-1,) + Y.shape
# Test fitting with different methods:
for fit_method in ['OLS', 'WLS', 'NLLS']:
tensor_model = dti.TensorModel(gtab,
fit_method=fit_method)
tensor_fit = tensor_model.fit(Y)
assert_true(tensor_fit.model is tensor_model)
assert_equal(tensor_fit.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_fit.evals[0], evals)
assert_array_almost_equal(tensor_fit.quadratic_form[0], tensor,
err_msg=\
"Calculation of tensor from Y does not compare to analytical solution")
assert_almost_equal(tensor_fit.md[0], md)
assert_array_almost_equal(tensor_fit.mode, mode, decimal=5)
assert_equal(tensor_fit.directions.shape[-2], 1)
assert_equal(tensor_fit.directions.shape[-1], 3)
# Test error-handling:
assert_raises(ValueError,
dti.TensorModel,
gtab,
fit_method='crazy_method')
def test_tensor_model():
fdata, fbval, fbvec = get_data('small_25')
data1 = nib.load(fdata).get_data()
gtab1 = grad.gradient_table(fbval, fbvec)
data2, gtab2 = dsi_voxels()
for data, gtab in zip([data1, data2], [gtab1, gtab2]):
dm = dti.TensorModel(gtab, 'LS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.9, True)
dm = dti.TensorModel(gtab, 'WLS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.9, True)
assert_equal(dtifit.fa > 0, True)
sphere = create_unit_sphere(4)
assert_equal(len(dtifit.odf(sphere)), len(sphere.vertices))
# Check that the multivoxel case works:
dtifit = dm.fit(data)
# Check that it works on signal that has already been normalized to S0:
dm_to_relative = dti.TensorModel(gtab)
if np.any(gtab.b0s_mask):
relative_data = (data[0, 0, 0]/np.mean(data[0, 0, 0,
gtab.b0s_mask]))
dtifit_to_relative = dm_to_relative.fit(relative_data)
npt.assert_almost_equal(dtifit.fa[0, 0, 0], dtifit_to_relative.fa,
decimal=3)
# And smoke-test that all these operations return sensibly-shaped arrays:
assert_equal(dtifit.fa.shape, data.shape[:3])
assert_equal(dtifit.ad.shape, data.shape[:3])
assert_equal(dtifit.md.shape, data.shape[:3])
assert_equal(dtifit.rd.shape, data.shape[:3])
assert_equal(dtifit.trace.shape, data.shape[:3])
assert_equal(dtifit.mode.shape, data.shape[:3])
assert_equal(dtifit.linearity.shape, data.shape[:3])
assert_equal(dtifit.planarity.shape, data.shape[:3])
assert_equal(dtifit.sphericity.shape, data.shape[:3])
# Test for the shape of the mask
assert_raises(ValueError, dm.fit, np.ones((10, 10, 3)), np.ones((3, 3)))
# Make some synthetic data
b0 = 1000.
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
# The first b value is 0., so we take the second one:
B = bvals[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
A_squiggle = tensor - (1 / 3.0) * np.trace(tensor) * np.eye(3)
mode = (3 * np.sqrt(6) * np.linalg.det(A_squiggle /
np.linalg.norm(A_squiggle)))
evals_eigh, evecs_eigh = np.linalg.eigh(tensor)
# Sort according to eigen-value from large to small:
evecs = evecs_eigh[:, np.argsort(evals_eigh)[::-1]]
# Check that eigenvalues and eigenvectors are properly sorted through
# that previous operation:
for i in range(3):
assert_array_almost_equal(np.dot(tensor, evecs[:, i]),
evals[i] * evecs[:, i])
# Design Matrix
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
assert_almost_equal(Y[0], b0)
Y.shape = (-1,) + Y.shape
# Test fitting with different methods:
for fit_method in ['OLS', 'WLS', 'NLLS']:
tensor_model = dti.TensorModel(gtab,
fit_method=fit_method,
return_S0_hat=True)
tensor_fit = tensor_model.fit(Y)
assert_true(tensor_fit.model is tensor_model)
assert_equal(tensor_fit.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_fit.evals[0], evals)
assert_array_almost_equal(tensor_fit.S0_hat, b0, decimal=3)
# Test that the eigenvectors are correct, one-by-one:
for i in range(3):
# Eigenvectors have intrinsic sign ambiguity
# (see
# http://prod.sandia.gov/techlib/access-control.cgi/2007/076422.pdf)
# so we need to allow for sign flips. One of the following should
# always be true:
assert_(
np.all(np.abs(tensor_fit.evecs[0][:, i] -
evecs[:, i]) < 10e-6) or
np.all(np.abs(-tensor_fit.evecs[0][:, i] -
evecs[:, i]) < 10e-6))
# We set a fixed tolerance of 10e-6, similar to array_almost_equal
err_msg = "Calculation of tensor from Y does not compare to "
err_msg += "analytical solution"
assert_array_almost_equal(tensor_fit.quadratic_form[0], tensor,
err_msg=err_msg)
assert_almost_equal(tensor_fit.md[0], md)
assert_array_almost_equal(tensor_fit.mode, mode, decimal=5)
assert_equal(tensor_fit.directions.shape[-2], 1)
assert_equal(tensor_fit.directions.shape[-1], 3)
# Test error-handling:
assert_raises(ValueError,
dti.TensorModel,
gtab,
fit_method='crazy_method')
# Test custom fit tensor method
try:
model = dti.TensorModel(gtab, fit_method=lambda *args, **kwargs: 42)
fit = model.fit_method()
except Exception as exc:
assert False, "TensorModel should accept custom fit methods: %s" % exc
assert fit == 42, "Custom fit method for TensorModel returned %s." % fit
# Test multi-voxel data
data = np.zeros((3, Y.shape[1]))
# Normal voxel
data[0] = Y
# High diffusion voxel, all diffusing weighted signal equal to zero
data[1, gtab.b0s_mask] = b0
data[1, ~gtab.b0s_mask] = 0
# Masked voxel, all data set to zero
data[2] = 0.
tensor_model = dti.TensorModel(gtab)
fit = tensor_model.fit(data)
assert_array_almost_equal(fit[0].evals, evals)
# Return S0_test
tensor_model = dti.TensorModel(gtab, return_S0_hat=True)
fit = tensor_model.fit(data)
assert_array_almost_equal(fit[0].evals, evals)
assert_array_almost_equal(fit[0].S0_hat, b0)
# Evals should be high for high diffusion voxel
assert_(all(fit[1].evals > evals[0] * .9))
# Evals should be zero where data is masked
assert_array_almost_equal(fit[2].evals, 0.)
def test_TensorModel():
data, gtab = dsi_voxels()
dm = dti.TensorModel(gtab, 'LS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.5, True)
dm = dti.TensorModel(gtab, 'WLS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.5, True)
sphere = create_unit_sphere(4)
assert_equal(len(dtifit.odf(sphere)), len(sphere.vertices))
assert_almost_equal(dtifit.fa, gfa(dtifit.odf(sphere)), 1)
# Check that the multivoxel case works:
dtifit = dm.fit(data)
# And smoke-test that all these operations return sensibly-shaped arrays:
assert_equal(dtifit.fa.shape, data.shape[:3])
assert_equal(dtifit.ad.shape, data.shape[:3])
assert_equal(dtifit.md.shape, data.shape[:3])
assert_equal(dtifit.rd.shape, data.shape[:3])
assert_equal(dtifit.trace.shape, data.shape[:3])
assert_equal(dtifit.mode.shape, data.shape[:3])
assert_equal(dtifit.linearity.shape, data.shape[:3])
assert_equal(dtifit.planarity.shape, data.shape[:3])
assert_equal(dtifit.sphericity.shape, data.shape[:3])
# Test for the shape of the mask
assert_raises(ValueError, dm.fit, np.ones((10, 10, 3)), np.ones((3, 3)))
# Make some synthetic data
b0 = 1000.
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
# The first b value is 0., so we take the second one:
B = bvals[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
A_squiggle = tensor - (1 / 3.0) * np.trace(tensor) * np.eye(3)
mode = 3 * np.sqrt(6) * np.linalg.det(
A_squiggle / np.linalg.norm(A_squiggle))
evecs = np.linalg.eigh(tensor)[1]
# Design Matrix
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
assert_almost_equal(Y[0], b0)
Y.shape = (-1, ) + Y.shape
# Test fitting with different methods:
for fit_method in ['OLS', 'WLS', 'NLLS']:
tensor_model = dti.TensorModel(gtab, fit_method=fit_method)
tensor_fit = tensor_model.fit(Y)
assert_true(tensor_fit.model is tensor_model)
assert_equal(tensor_fit.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_fit.evals[0], evals)
assert_array_almost_equal(tensor_fit.quadratic_form[0], tensor,
err_msg=\
"Calculation of tensor from Y does not compare to analytical solution")
assert_almost_equal(tensor_fit.md[0], md)
assert_array_almost_equal(tensor_fit.mode, mode, decimal=5)
assert_equal(tensor_fit.directions.shape[-2], 1)
assert_equal(tensor_fit.directions.shape[-1], 3)
# Test error-handling:
assert_raises(ValueError, dti.TensorModel, gtab, fit_method='crazy_method')
def test_wls_and_ls_fit():
"""
Tests the WLS and LS fitting functions to see if they returns the correct
eigenvalues and eigenvectors.
Uses data/55dir_grad.bvec as the gradient table and 3by3by56.nii
as the data.
"""
# Defining Test Voxel (avoid nibabel dependency) ###
# Recall: D = [Dxx,Dyy,Dzz,Dxy,Dxz,Dyz,log(S_0)] and D ~ 10^-4 mm^2 /s
b0 = 1000.
bvec, bval = read_bvec_file(get_data('55dir_grad.bvec'))
B = bval[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
# Design Matrix
gtab = grad.gradient_table(bval, bvec)
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
assert_almost_equal(Y[0], b0)
Y.shape = (-1,) + Y.shape
# Testing WLS Fit on Single Voxel
# If you do something wonky (passing min_signal<0), you should get an
# error:
npt.assert_raises(ValueError, TensorModel, gtab, fit_method='WLS',
min_signal=-1)
# Estimate tensor from test signals
model = TensorModel(gtab, fit_method='WLS', return_S0_hat=True)
tensor_est = model.fit(Y)
assert_equal(tensor_est.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_est.evals[0], evals)
assert_array_almost_equal(tensor_est.quadratic_form[0], tensor,
err_msg="Calculation of tensor from Y does not "
"compare to analytical solution")
assert_almost_equal(tensor_est.md[0], md)
assert_array_almost_equal(tensor_est.S0_hat[0], b0, decimal=3)
# Test that we can fit a single voxel's worth of data (a 1d array)
y = Y[0]
tensor_est = model.fit(y)
assert_equal(tensor_est.shape, tuple())
assert_array_almost_equal(tensor_est.evals, evals)
assert_array_almost_equal(tensor_est.quadratic_form, tensor)
assert_almost_equal(tensor_est.md, md)
assert_array_almost_equal(tensor_est.lower_triangular(b0), D)
# Test using fit_method='LS'
model = TensorModel(gtab, fit_method='LS')
tensor_est = model.fit(y)
assert_equal(tensor_est.shape, tuple())
assert_array_almost_equal(tensor_est.evals, evals)
assert_array_almost_equal(tensor_est.quadratic_form, tensor)
assert_almost_equal(tensor_est.md, md)
assert_array_almost_equal(tensor_est.lower_triangular(b0), D)
assert_array_almost_equal(tensor_est.linearity, linearity(evals))
assert_array_almost_equal(tensor_est.planarity, planarity(evals))
assert_array_almost_equal(tensor_est.sphericity, sphericity(evals))
d = [1, 1, 1]
d[0:len(shape)] = shape
else:
d = shape
return np.mgrid[0:d[0], 0:d[1], 0:d[2]]
if __name__ == '__main__':
import dipy.core.qball as qball
from dipy.io.bvectxt import read_bvec_file
filename = '/Users/bagrata/HARDI/E1322S8I1.nii.gz'
grad_table_filename = '/Users/bagrata/HARDI/E1322S8I1.bvec'
from nipy import load_image, save_image
grad_table, b_values = read_bvec_file(grad_table_filename)
img = load_image(filename)
print 'input dimensions: '
print img.ndim
print 'image size: '
print img.shape
print 'image affine: '
print img.affine
print 'images has pixels with size: '
print np.dot(img.affine, np.eye(img.ndim + 1)).diagonal()[0:3]
data = np.asarray(img)
theta, phi = np.mgrid[0:2 * np.pi:64 * 1j, 0:np.pi:32 * 1j]
odf_i = qball.ODF(data[188:192, 188:192, 22:24, :], 4, grad_table,
b_values)
disp_odf(odf_i[0:1, 0:2, 0:2])
def test_tensor_model():
fdata, fbval, fbvec = get_data('small_25')
data = nib.load(fdata).get_data()
gtab = grad.gradient_table(fbval, fbvec)
dm = dti.TensorModel(gtab, 'LS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.9, True)
dm = dti.TensorModel(gtab, 'WLS')
dtifit = dm.fit(data[0, 0, 0])
assert_equal(dtifit.fa < 0.9, True)
assert_equal(dtifit.fa > 0, True)
sphere = create_unit_sphere(4)
assert_equal(len(dtifit.odf(sphere)), len(sphere.vertices))
# Check that the multivoxel case works:
dtifit = dm.fit(data)
# Check that it works on signal that has already been normalized to S0:
dm_to_relative = dti.TensorModel(gtab)
relative_data = (data[0, 0, 0]/np.mean(data[0, 0, 0, gtab.b0s_mask]))
dtifit_to_relative = dm_to_relative.fit(relative_data)
npt.assert_almost_equal(dtifit.fa[0,0,0], dtifit_to_relative.fa, decimal=3)
# And smoke-test that all these operations return sensibly-shaped arrays:
assert_equal(dtifit.fa.shape, data.shape[:3])
assert_equal(dtifit.ad.shape, data.shape[:3])
assert_equal(dtifit.md.shape, data.shape[:3])
assert_equal(dtifit.rd.shape, data.shape[:3])
assert_equal(dtifit.trace.shape, data.shape[:3])
assert_equal(dtifit.mode.shape, data.shape[:3])
assert_equal(dtifit.linearity.shape, data.shape[:3])
assert_equal(dtifit.planarity.shape, data.shape[:3])
assert_equal(dtifit.sphericity.shape, data.shape[:3])
# Test for the shape of the mask
assert_raises(ValueError, dm.fit, np.ones((10, 10, 3)), np.ones((3,3)))
# Make some synthetic data
b0 = 1000.
bvecs, bvals = read_bvec_file(get_data('55dir_grad.bvec'))
gtab = grad.gradient_table_from_bvals_bvecs(bvals, bvecs.T)
# The first b value is 0., so we take the second one:
B = bvals[1]
# Scale the eigenvalues and tensor by the B value so the units match
D = np.array([1., 1., 1., 0., 0., 1., -np.log(b0) * B]) / B
evals = np.array([2., 1., 0.]) / B
md = evals.mean()
tensor = from_lower_triangular(D)
A_squiggle = tensor - (1 / 3.0) * np.trace(tensor) * np.eye(3)
mode = 3 * np.sqrt(6) * np.linalg.det(A_squiggle / np.linalg.norm(A_squiggle))
evecs = np.linalg.eigh(tensor)[1]
# Design Matrix
X = dti.design_matrix(gtab)
# Signals
Y = np.exp(np.dot(X, D))
assert_almost_equal(Y[0], b0)
Y.shape = (-1,) + Y.shape
# Test fitting with different methods:
for fit_method in ['OLS', 'WLS', 'NLLS']:
tensor_model = dti.TensorModel(gtab,
fit_method=fit_method)
tensor_fit = tensor_model.fit(Y)
assert_true(tensor_fit.model is tensor_model)
assert_equal(tensor_fit.shape, Y.shape[:-1])
assert_array_almost_equal(tensor_fit.evals[0], evals)
assert_array_almost_equal(tensor_fit.quadratic_form[0], tensor,
err_msg=\
"Calculation of tensor from Y does not compare to analytical solution")
assert_almost_equal(tensor_fit.md[0], md)
assert_array_almost_equal(tensor_fit.mode, mode, decimal=5)
assert_equal(tensor_fit.directions.shape[-2], 1)
assert_equal(tensor_fit.directions.shape[-1], 3)
# Test error-handling:
assert_raises(ValueError,
dti.TensorModel,
gtab,
fit_method='crazy_method')
# Test multi-voxel data
data = np.zeros((3, Y.shape[1]))
# Normal voxel
data[0] = Y
# High diffusion voxel, all diffusing weighted signal equal to zero
data[1, gtab.b0s_mask] = b0
data[1, ~gtab.b0s_mask] = 0
# Masked voxel, all data set to zero
data[2] = 0.
tensor_model = dti.TensorModel(gtab)
fit = tensor_model.fit(data)
assert_array_almost_equal(fit[0].evals, evals)
# Evals should be high for high diffusion voxel
assert_(all(fit[1].evals > evals[0] * .9))
# Evals should be zero where data is masked
assert_array_almost_equal(fit[2].evals, 0.)